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1.  Sex-Specific Immunization for Sexually Transmitted Infections Such as Human Papillomavirus: Insights from Mathematical Models 
PLoS Medicine  2011;8(12):e1001147.
Johannes Bogaards and colleagues use mathematical models to investigate whether vaccinating females only, males only, or both sexes is the best way to achieve the most effective reduction in the population prevalence of sexually-transmitted infections
Background
Sex-specific differences regarding the transmissibility and the course of infection are the rule rather than the exception in the epidemiology of sexually transmitted infections (STIs). Human papillomavirus (HPV) provides an example: disease outcomes differ between men and women, as does the potential for transmission to the opposite sex. HPV vaccination of preadolescent girls was recently introduced in many countries, and inclusion of boys in the vaccination programs is being discussed. Here, we address the question of whether vaccinating females only, males only, or both sexes is the most effective strategy to reduce the population prevalence of an STI like HPV.
Methods and Findings
We use a range of two-sex transmission models with varying detail to identify general criteria for allocating a prophylactic vaccine between both sexes. The most effective reduction in the population prevalence of infection is always achieved by single-sex vaccination; vaccinating the sex with the highest prevaccine prevalence is the preferred strategy in most circumstances. Exceptions arise only when the higher prevaccine prevalence is due to a substantially lower rate of natural immunity, or when natural immunity is lifelong, and a prolonged duration of infectiousness coincides with increased transmissibility. Predictions from simple models were confirmed in simulations based on an elaborate HPV transmission model. Our analysis suggests that relatively inefficient genital transmission from males to females might render male vaccination more effective in reducing overall infection levels. However, most existing HPV vaccination programs have achieved sufficient coverage to continue with female-only vaccination.
Conclusions
Increasing vaccine uptake among preadolescent girls is more effective in reducing HPV infection than including boys in existing vaccination programs. As a rule, directing prophylactic immunization at the sex with the highest prevaccine prevalence results in the largest reduction of the population prevalence.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
About 10% of cancers in women occur in the cervix, the structure that connects the womb to the vagina. Every year, more than a quarter of a million women (85% of them in developing countries) die because of cervical cancer, which only occurs after the cervix has been infected with a human papillomavirus (HPV) through sexual intercourse (HPV is one of more than thirty sexually transmissable organisms that, globally, cause many millions of sexually transmitted infections every year). There are many types of HPV, a virus that infects the skin and the mucosa (the moist membranes that line various parts of the body, including the cervix). Most people become infected with HPV at some time during their life, but most never know they have been infected. Some HPV types cause harmless warts on the skin or around the genital area, and several—in particular HPV16 and HPV18, so-called high-risk HPVs—can cause cervical cancer (and some other cancers, including anal, penile, head, and neck cancers). HPV infections are usually cleared by the immune system, but about 10% of women infected with a high-risk HPV develop a long-term infection that puts them at risk of developing cervical cancer.
Why Was This Study Done?
Screening programs have greatly reduced cervical cancer deaths in developed countries by detecting the cancer early, when it can be treated. However, it would be better to prevent cervical cancer ever developing. Moreover, most women in developing countries do not have access to screening. Because infection with specific HPV types can cause the development of some types of cervical cancer, vaccination of girls against HPV before the onset of sexual activity might be one way to prevent cervical cancer. Scientists recently developed a vaccine that prevents infection with HPV16 and HPV18, and HPV vaccination programs have been introduced in several countries. These programs are currently directed only at girls because HPV-related illness and death are higher among women than men, but should boys also be included in HPV vaccination programs? Men would benefit directly from immunization against HPV-related diseases, but, in addition, vaccination of boys might help to reduce the circulation of HPV in the population, thereby indirectly improving the protection of women through so-called “herd immunity.” In this study, the researchers used mathematical models to investigate whether vaccinating girls only, boys only, or both sexes is the most effective way to reduce the population prevalence of HPV infection (the proportion of the population infected with HPV).
What Did the Researchers Do and Find?
The researchers first used a range of standard two-sex mathematical models of infection and transmission in heterosexual populations to identify general criteria for allocating an HPV vaccine between the sexes. They found that the most effective reduction in the population prevalence of HPV infection was always achieved by single-sex vaccination and that, in most situations, the preferred strategy was to vaccinate the sex with the highest prevaccine prevalence of HPV infection. The researchers confirmed these predictions using a more elaborate HPV transmission model that incorporated differences among individuals in age and level of sexual activity. Importantly, this second analysis also suggested that for existing girl-only vaccination programs, increasing coverage of vaccination among girls would bolster herd immunity more effectively than switching to a policy of vaccinating both sexes.
What Do These Findings Mean?
The findings of this study suggest that increasing vaccine uptake among preadolescent girls is a more effective way to reduce HPV infection than including boys in existing vaccination programs. They also suggest that directing HPV vaccination at the sex with the highest prevaccine prevalence of infection will reduce the population prevalence of HPV most effectively. Although the accuracy of these findings is dependent on the assumptions included in the mathematical transmission models used by the researchers, these findings support a policy of increasing female HPV vaccine coverage as far as possible, within the limits set by vaccine acceptance and economic constraints. More generally, these findings suggest that single-sex preventative interventions might be the best way to reduce heterosexual transmission of other sexually transmitted infections and that targeting the sex with the highest prevalence of infection might achieve the most effective reduction in the population prevalence of these common diseases.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001147.
The US National Cancer Institute provides information about cervical cancer for patients and for health professionals, including information on HPV vaccines (in English and Spanish)
The US Centers for Disease Control and Prevention also has information about cervical cancer and HPV
The UK National Health Service Choices website has pages on cervical cancer and HPV vaccination (available in several languages and including a short video of girls talking about HPV vaccination)
The PREHDICT project investigates health-economic modeling of prevention strategies for HPV-related diseases in European countries; information about this project is available from the European Cervical Cancer Association
More information about cervical cancer and HPV vaccination is available from Macmillan Cancer Support
Personal stories about cervical cancer are available through the charity Healthtalkonline
MedlinePlus provides links to additional resources about cervical cancer and other sexually transmitted infections (in English and Spanish)
doi:10.1371/journal.pmed.1001147
PMCID: PMC3243713  PMID: 22205887
2.  A Population-Based Evaluation of a Publicly Funded, School-Based HPV Vaccine Program in British Columbia, Canada: Parental Factors Associated with HPV Vaccine Receipt 
PLoS Medicine  2010;7(5):e1000270.
Analysis of a telephone survey by Gina Ogilvie and colleagues identifies the parental factors associated with HPV vaccine uptake in a school-based program in Canada.
Background
Information on factors that influence parental decisions for actual human papillomavirus (HPV) vaccine receipt in publicly funded, school-based HPV vaccine programs for girls is limited. We report on the level of uptake of the first dose of the HPV vaccine, and determine parental factors associated with receipt of the HPV vaccine, in a publicly funded school-based HPV vaccine program in British Columbia, Canada.
Methods and Findings
All parents of girls enrolled in grade 6 during the academic year of September 2008–June 2009 in the province of British Columbia were eligible to participate. Eligible households identified through the provincial public health information system were randomly selected and those who consented completed a validated survey exploring factors associated with HPV vaccine uptake. Bivariate and multivariate analyses were conducted to calculate adjusted odds ratios to identify the factors that were associated with parents' decision to vaccinate their daughter(s) against HPV. 2,025 parents agreed to complete the survey, and 65.1% (95% confidence interval [CI] 63.1–67.1) of parents in the survey reported that their daughters received the first dose of the HPV vaccine. In the same school-based vaccine program, 88.4% (95% CI 87.1–89.7) consented to the hepatitis B vaccine, and 86.5% (95% CI 85.1–87.9) consented to the meningococcal C vaccine. The main reasons for having a daughter receive the HPV vaccine were the effectiveness of the vaccine (47.9%), advice from a physician (8.7%), and concerns about daughter's health (8.4%). The main reasons for not having a daughter receive the HPV vaccine were concerns about HPV vaccine safety (29.2%), preference to wait until the daughter is older (15.6%), and not enough information to make an informed decision (12.6%). In multivariate analysis, overall attitudes to vaccines, the impact of the HPV vaccine on sexual practices, and childhood vaccine history were predictive of parents having a daughter receive the HPV vaccine in a publicly funded school-based HPV vaccine program. By contrast, having a family with two parents, having three or more children, and having more education was associated with a decreased likelihood of having a daughter receive the HPV vaccine.
Conclusions
This study is, to our knowledge, one of the first population-based assessments of factors associated with HPV vaccine uptake in a publicly funded school-based program worldwide. Policy makers need to consider that even with the removal of financial and health care barriers, parents, who are key decision makers in the uptake of this vaccine, are still hesitant to have their daughters receive the HPV vaccine, and strategies to ensure optimal HPV vaccine uptake need to be employed.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
About 10% of cancers in women occur in the cervix, the structure that connects the womb to the vagina. Every year, globally, more than a quarter of a million women die because of cervical cancer, which only occurs after the cervix has been infected with a human papillomavirus (HPV) through sexual intercourse. There are many types of HPV, a virus that infects the skin and the mucosa (the moist membranes that line various parts of the body, including the cervix). Although most people become infected with HPV at some time in their life, most never know they are infected. However, some HPV types cause harmless warts on the skin or around the genital area and several—in particular, HPV 16 and HPV 18, so-called high-risk HPVs—can cause cervical cancer. HPV infections are usually cleared by the immune system, but about 10% of women infected with a high-risk HPV develop a long-term infection that puts them at risk of developing cervical cancer.
Why Was This Study Done?
Screening programs have greatly reduced cervical cancer deaths in developed countries in recent decades by detecting the cancer early when it can be treated; but it would be better to prevent cervical cancer ever developing. Because HPV is necessary for the development of cervical cancer, vaccination of girls against HPV infection before the onset of sexual activity might be one way to do this. Scientists recently developed a vaccine that prevents infection with HPV 16 and HPV 18 (and with two HPVs that cause genital warts) and that should, therefore, reduce the incidence of cervical cancer. Publicly funded HPV vaccination programs are now planned or underway in several countries; but before girls can receive the HPV vaccine, parental consent is usually needed, so it is important to know what influences parental decisions about HPV vaccination. In this study, the researchers undertake a telephone survey to determine the uptake of the HPV vaccine by 11-year-old girls (grade 6) in British Columbia, Canada, and to determine the parental factors associated with vaccine uptake; British Columbia started a voluntary school-based HPV vaccine program in September 2008.
What Did the Researchers Do and Find?
In early 2009, the researchers contacted randomly selected parents of girls enrolled in grade 6 during the 2008–2009 academic year and asked them to complete a telephone survey that explored factors associated with HPV vaccine uptake. 65.1% of the 2,025 parents who completed the survey had consented to their daughter receiving the first dose of HPV vaccine. By contrast, more than 85% of the parents had consented to hepatitis B and meningitis C vaccination of their daughters. Nearly half of the parents surveyed said their main reason for consenting to HPV vaccination was the effectiveness of the vaccine. Conversely, nearly a third of the parents said concern about the vaccine's safety was their main reason for not consenting to vaccination and one in eight said they had been given insufficient information to make an informed decision. In a statistical analysis of the survey data, the researchers found that a positive parental attitude towards vaccination, a parental belief that HPV vaccination had limited impact on sexual practices, and completed childhood vaccination increased the likelihood of a daughter receiving the HPV vaccine. Having a family with two parents or three or more children and having well-educated parents decreased the likelihood of a daughter receiving the vaccine.
What Do These Findings Mean?
These findings provide one of the first population-based assessments of the factors that affect HPV vaccine uptake in a setting where there are no financial or health care barriers to vaccination. By identifying the factors associated with parental reluctance to agree to HPV vaccination for their daughters, these findings should help public-health officials design strategies to ensure optimal HPV vaccine uptake, although further studies are needed to discover why, for example, parents with more education are less likely to agree to vaccination than parents with less education. Importantly, the findings of this study, which are likely to be generalizable to other high-income countries, indicate that there is a continued need to ensure that the public receives credible, clear information about both the benefits and long-term safety of HPV vaccination.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000270.
The US National Cancer Institute provides information about cervical cancer for patients and for health professionals, including information on HPV vaccines (in English and Spanish)
The US Centers for Disease Control and Prevention also has information about cervical cancer and about HPV
The UK National Health Service Choices website has pages on cervical cancer and on HPV vaccination
More information about cervical cancer and HPV vaccination is available from the Macmillan cancer charity
ImmunizeBC provides general information about vaccination and information about HPV vaccination in British Columbia
MedlinePlus provides links to additional resources about cervical cancer (in English and Spanish)
doi:10.1371/journal.pmed.1000270
PMCID: PMC2864299  PMID: 20454567
3.  Prevalence, Acquisition, and Clearance of Cervical Human Papillomavirus Infection among Women with Normal Cytology: Hawaii Human Papillomavirus Cohort Study 
Cancer research  2008;68(21):8813-8824.
Few natural history studies of cervical human papillomavirus (HPV) incidence and duration have been conducted among older women, especially from multiethnic populations. Viral and nonviral determinants of HPV acquisition and clearance were examined among 972 sexually active women, ages 18 to 85 years, recruited from clinics on Oahu, Hawaii, and followed for a mean duration of 15 months (range, 2–56 months). Interviews and cervical cell specimens for cytology and HPV DNA detection by PCR, using the PGMY09/PGMY11 primer system, were obtained at baseline and at 4-month intervals. The prevalence of cervical HPV infection was 25.6% at study entry. A total of 476 incident genotype-specific infections were observed during the follow-up period. The incidence of high-risk (HR) HPV types (9.26 per 1,000 woman-months) was similar to low-risk (LR) HPV types (8.24 per 1,000 woman-months). The most commonly acquired HR-HPV types were HPV-52, HPV-16, and HPV-31; and their incidence was increased significantly with a coexisting cervical HPV infection. Cervical HPV acquisition decreased with age, income, and long-term use of oral contraceptives and increased with number of sexual partners, use of hormonal creams, alcohol drinking, and condom use by a sexual partner. Cohort participants cleared 265 of the 476 incident infections during follow-up. LR-HPV infections cleared more rapidly than did HR-HPV infections (median, 180 days versus 224 days). Clearance times were enhanced among older women and women with multiple infections. Our data suggest several viral and nonviral determinants of cervical HPV acquisition and clearance that might be used in cervical cancer prevention programs.
doi:10.1158/0008-5472.CAN-08-1380
PMCID: PMC2727731  PMID: 18974124
4.  Epidemiology of HPV 16 and Cervical Cancer in Finland and the Potential Impact of Vaccination: Mathematical Modelling Analyses 
PLoS Medicine  2006;3(5):e138.
Background
Candidate human papillomavirus (HPV) vaccines have demonstrated almost 90%-100% efficacy in preventing persistent, type-specific HPV infection over 18 mo in clinical trials. If these vaccines go on to demonstrate prevention of precancerous lesions in phase III clinical trials, they will be licensed for public use in the near future. How these vaccines will be used in countries with national cervical cancer screening programmes is an important question.
Methods and Findings
We developed a transmission model of HPV 16 infection and progression to cervical cancer and calibrated it to Finnish HPV 16 seroprevalence over time. The model was used to estimate the transmission probability of the virus, to look at the effect of changes in patterns of sexual behaviour and smoking on age-specific trends in cancer incidence, and to explore the impact of HPV 16 vaccination. We estimated a high per-partnership transmission probability of HPV 16, of 0.6. The modelling analyses showed that changes in sexual behaviour and smoking accounted, in part, for the increase seen in cervical cancer incidence in 35- to 39-y-old women from 1990 to 1999. At both low (10% in opportunistic immunisation) and high (90% in a national immunisation programme) coverage of the adolescent population, vaccinating women and men had little benefit over vaccinating women alone. We estimate that vaccinating 90% of young women before sexual debut has the potential to decrease HPV type-specific (e.g., type 16) cervical cancer incidence by 91%. If older women are more likely to have persistent infections and progress to cancer, then vaccination with a duration of protection of less than 15 y could result in an older susceptible cohort and no decrease in cancer incidence. While vaccination has the potential to significantly reduce type-specific cancer incidence, its combination with screening further improves cancer prevention.
Conclusions
HPV vaccination has the potential to significantly decrease HPV type-specific cervical cancer incidence. High vaccine coverage of women alone, sustained over many decades, with a long duration of vaccine-conferred protection, would have the greatest impact on type-specific cancer incidence. This level of coverage could be achieved through national coordinated programmes, with surveillance to detect cancers caused by nonvaccine oncogenic HPV types.
Using a mathematical model of transmission of HPV 16 infection and progression to cervical cancer, Ruanne Barnabas and colleagues show that HPV vaccination could significantly decrease HPV type-specific cervical cancer incidence.
doi:10.1371/journal.pmed.0030138
PMCID: PMC1434486  PMID: 16573364
5.  Human papillomavirus (HPV) vaccination for the prevention of HPV 16/18 induced cervical cancer and its precursors 
Introduction
Essential precondition for the development of cervical cancer is a persistent human papillomavirus (HPV) infection. The majority - approximately 70% - of cervical carcinomas is caused by two high-risk HPV types (16 and 18). Recently, two vaccines have been approved to the German market with the potential to induce protection against HPV 16 and HPV 18 among additional low-risk virus types.
Objectives
To analyse whether HPV vaccination is effective with regard to the reduction of cervical cancer and precursors of cervical carcinoma (CIN), respectively? Does HPV vaccination represent a cost-effective alternative or supplement to present screening practice? Are there any differences concerning cost-effectiveness between the two available vaccines? Should HPV vaccination be recommended from a health economic point of view? If so, which recommendations can be conveyed with respect to a (re)organization of the German vaccination strategy? Which ethical, social and legal implications have to be considered?
Methods
Based on a systematic literature review, randomized controlled trials (RCT) looking at the effectiveness of HPV vaccination for the prevention of cervical carcinoma and its precursors - cervical intraepithelial neoplasia - have been identified. In addition, health economic models were identified to address the health economic research questions. Quality assessment of medical and economic literature was assured by application of general assessment standards for the systematic and critical appraisal of scientific studies.
Results
Vaccine efficacy in prevention of CIN 2 or higher lesions in HPV 16 or HPV 18 negative women, who received all vaccination doses, ranges between 98% and 100%. Side effects of the vaccination are mainly associated with injection site reactions (redness, turgor, pain). No significant differences concerning serious complications between the vaccination- and the placebo-groups were reported. Results of base case scenarios in the identified health economic modeling analyses range from approximately 3,000 Euro to 40,000 Euro per additional QALY (QALY = Quality-adjusted life year) and approximately 9,000 Euro to 65,000 Euro per additional life year (LYG), respectively.
Discussion
The included studies show that both available HPV vaccines are effective in preventing HPV 16 and HPV 18 infections and probable resulting premalignant lesions of the cervix. However, the duration of protection is currently unclear. With regard to side effects, the vaccination can be considered as secure. Nevertheless, the number of cases within the clinical studies is not sufficient to determine the occurrence of rarely occurring (severe) adverse events in a reliable way. A reduction in the incidence and induced mortality through cervical cancer in Germany is not only depending on the vaccine’s clinical efficacy. Effects of the new technology on the overall participation rate in screening programs and the resulting vaccination rate and immunization status are also important factors. The results of identified health economic models vary substantially due to the heterogeneity of methodological approaches as well as chosen input parameters. However, almost all model-based analyses reached the conclusion that the implementation of a vaccination with lifelong protection can be considered as cost-effective, if the present screening practice continues. A comparison of the two vaccines shows, that the cost effectiveness ratios are more favorable with the quadrivalent vaccine than with the bivalent alternative when considering QALY as primary outcome parameter. The reason for this finding might be that in the case of the quadrivalent vaccine the prevention of genital warts can also be incorporated into the analysis. Variations of the duration of protection as well as the discounting rate were identified as the primary influencing factors of cost-effectiveness results.
Conclusion
Implementation of HPV vaccination might lead to a reduction of cervical cancer in immunized women. However, uptake of immunization should be accompanied by further studies in order to assess long-term effectiveness and safety aiming at an optimization of possible implementation processes. High numbers of participants are of particular importance regarding immunization. This has to be backed up by programs to optimize early detection – as this affects even those women who already underwent immunization. Since cost-effectiveness evidence might be significantly affected by the unclear duration of protective benefits, a final verdict on the vaccination’s cost-effectiveness in the German setting is not possible. Hence, risk-sharing-agreements between third-party payers and manufacturers would pose an option to balance the consequences of uncertainty towards the duration of protection on cost-effectiveness.
doi:10.3205/hta000066
PMCID: PMC3011291  PMID: 21289891
6.  Epidemiology of HPV genotypes in Uganda and the role of the current preventive vaccines: A systematic review 
Background
Limited data are available on the distribution of human papillomavirus (HPV) genotypes in the general population and in invasive cervical cancer (ICC) in Uganda. Yet, with the advent of preventive HPV vaccines that target HPV 16 and 18 responsible for causing about 70% of ICC cases in the world, such information is crucial to predict how vaccination and HPV-based screening will influence prevention of ICC.
Methods
To review the distribution of HPV infection and prevalent genotypes, electronic databases (e.g. PubMed/MEDLINE and HINARI) were searched for peer reviewed English articles on HPV infection up to November 30, 2010. Eligible studies were selected according to the following criteria: DNA-confirmed cervical or male genital HPV prevalence and genotypes, HPV incidence estimates and HPV seroprevalence among participants.
Results
Twenty studies were included in the review. Among HIV negative adult women, the prevalence of HR-HPV infections ranged from 10.2% -40.0% compared to 37.0% -100.0% among HIV positive women. Among HIV positive young women aged below 25 years, the prevalence of HR-HPV genotypes ranged from 41.6% -75.0% compared to 23.7% -67.1% among HIV negative women. Multiple infections with non vaccine HR-HPV genotypes were frequent in both HIV positive and HIV negative women. The main risk factors for prevalent HPV infections were age, lifetime number of sexual partners and HIV infection. Incident infections with HR-HPV genotypes were more frequent among adult HIV positive than HIV negative women estimated at 17.3 and 7.0 per 100 person-years, respectively. Similarly, incident HR-HPV among young women aged below 25 years were more frequent among HIV positive (40.0 per 100 person-years) than HIV negative women (20.3 per 100 person-years) women. The main risk factor for incident infection was HIV infection. HPV 16 and 18 were the most common genotypes in ICC with HPV 16/18 contributing up to 73.5% of cases with single infections.
Among uncircumcised adult HIV positive males, HR-HPV prevalence ranged from 55.3% -76.6% compared to 38.6% -47.6% in HIV negative males. Incident and multiple HR-HPV infections were frequent in HIV positive males. Being uncircumcised was the main risk factor for both prevalent and incident HPV infection.
Conclusion
Infections with HR-HPV genotypes were very common particularly among HIV positive individuals and young women irrespective of HIV status. Given the high prevalence of HIV infection, HPV-associated conditions represent a major public health burden in Uganda. However, although the most common HPV genotypes in ICC cases in Uganda were those targeted by current preventive vaccines, there were a large number of individuals infected with other HR-HPV genotypes. Technology allowing, these other HR-HPV types should be considered in the development of the next generation of vaccines.
doi:10.1186/1750-9378-6-11
PMCID: PMC3163594  PMID: 21749691
7.  Type specific persistence of high risk human papillomavirus (HPV) as indicator of high grade cervical squamous intraepithelial lesions in young women: population based prospective follow up study 
BMJ : British Medical Journal  2002;325(7364):572.
Objectives
To investigate the role of human papillomavirus (HPV) in the development of cervical neoplasia in women with no previous cervical cytological abnormalities; whether the presence of virus DNA predicts development of squamous intraepithelial lesion; and whether the risk of incident squamous intraepithelial lesions differs with repeated detection of the same HPV type versus repeated detection of different types.
Design
Population based prospective cohort study.
Setting
General population in Copenhagen, Denmark.
Participants
10 758 women aged 20-29 years followed up for development of cervical cytological abnormalities; 370 incident cases were detected (40 with atypical squamous cells of undetermined significance, 165 with low grade squamous intraepithelial lesions, 165 with high grade squamous intraepithelial lesions).
Main outcome measures
Results of cervical smear tests and cervical swabs at enrolment and at the second examination about two years later.
Results
Compared with women who were negative for human papillomavirus at enrolment, those with positive results had a significantly increased risk at follow up of having atypical cells (odds ratio 3.2, 95% confidence interval 1.3 to 7.9), low grade lesions (7.5, 4.8 to 11.7), or high grade lesions (25.8, 15.3 to 43.6). Similarly, women who were positive for HPV at the second examination had a strongly increased risk of low (34.3, 17.6 to 67.0) and high grade lesions (60.7, 25.5 to 144.0). For high grade lesions the risk was strongly increased if the same virus type was present at both examinations (813.0, 168.2 to 3229.2).
Conclusions
Infection with human papillomavirus precedes the development of low and high grade squamous intraepithelial lesions. For high grade lesions the risk is greatest in women positive for the same type of HPV on repeated testing.
What is already known on this topicPersistence of infection with human papillomavirus (HPV) is thought to have a role in the development of cervical neoplasiaPrevious studies have included only a few cases of high grade squamous intraepithelial lesions, and few have randomly sampled women from the general populationWhat this study addsIn women aged 20-29, HPV infection preceded the development of high grade lesionsPersistent HPV infection with a specific HPV type was an indicator of incident high grade lesions among young women in the general populationThe association between persistence and high grade cervical lesions was more pronounced among women aged over 25
PMCID: PMC124551  PMID: 12228133
8.  Long-term Absolute Risk of Cervical Intraepithelial Neoplasia Grade 3 or Worse Following Human Papillomavirus Infection: Role of Persistence 
Background
Infection with high-risk human papillomavirus (HPV) is the main cause of high-grade cervical intraepithelial neoplasia (CIN) and cancer. It has been suggested that information about high-risk HPV type–specific infection might make cervical cancer screening more effective. Persistent HPV infection could also be a useful screening marker. We estimated the long-term risk of high-grade CIN after one-time detection of high-risk HPV DNA and after persistent infection with individual high-risk HPV types.
Methods
A cohort of 8656 women from the general population of Denmark was examined twice, 2 years apart (first study examination: May 15, 1991, to January 31, 1993; second study examination: October 1, 1993, to January 31, 1995). The women underwent a gynecological examination and cervical cytology and had swabs taken for HPV DNA analysis by the Hybrid Capture 2 and line probe assays. The women were followed up through the nationwide Danish Pathology Data Bank for cervical neoplasia for up to 13.4 years. The absolute risk of developing cervical lesions before a given time was estimated as a function of time.
Results
For women with normal cytological findings who were concurrently HPV16 DNA positive at the second examination, the estimated probability of developing CIN grade 3 (CIN3) or worse within 12 years of follow-up was 26.7% (95% confidence interval [CI] = 21.1% to 31.8%). The corresponding risks among those infected with HPV18 was 19.1% (95% CI = 10.4% to 27.3%), with HPV31 was 14.3% (95% CI = 9.1% to 19.4%), and with HPV33 was 14.9% (95% CI = 7.9% to 21.1%). The absolute risk of CIN3 or worse after infection with high-risk HPV types other than HPV16, HPV18, HPV31, or HPV33 was 6.0% (95% CI = 3.8% to 8.3%). The estimated absolute risk for CIN3 or cancer within 12 years of the second examination among women who were HPV16 DNA positive at both examinations was 47.4% (95% CI = 34.9% to 57.5%); by contrast, the risk of CIN3 or worse following a negative Hybrid Capture 2 test was 3.0% (95% CI = 2.5% to 3.5%).
Conclusion
HPV16, HPV18, HPV31, and HPV33 infection and especially HPV16 persistence were associated with high absolute risks for progression to high-grade cervical lesions. The results indicate the potential value of genotyping in cervical cancer screening. Given that HPV DNA–negative women retained their low risk of CIN3 or worse for many years, frequent screening of these women may be unnecessary.
doi:10.1093/jnci/djq356
PMCID: PMC2950170  PMID: 20841605
9.  Duration and Clearance of Anal Human Papillomavirus Infection among Women: the Hawaii HPV Cohort Study 
Background
The association of anal cancer with human papillomavirus (HPV) infection is well established; however, little is known about epidemiology of anal HPV in healthy women. We investigated patterns of duration and clearance of anal HPV infection in a cohort of healthy women in Hawaii.
Methods
Viral and non-viral determinants of anal HPV clearance were examined through a longitudinal cohort study of 431 sexually active women. At baseline and at 4-month intervals, interviews were conducted and cervical and anal cell specimens were obtained for HPV DNA detection.
Results
Fifty percent of the 431 women experienced a total of 414 incident anal HPV infections at one or more clinic visits from baseline through an average 1.2 year follow-up period. Of these infections, 58% cleared during follow-up. The clearance rate for a high-risk (HR) anal infection was 9.2 (95% confidence interval (CI): 6.9–11.9) per 100 woman-months with a median duration of 150 days (95% CI: 132–243 days). The slowest clearing HR-HPV types were HPV-59 (median, 350 days) and HPV-58 (median, 252 days). Median clearance times for HPV-16 and -18, the predominant types associated with anal cancer, were 132 days and 212 days, respectively. Non-viral factors that delayed clearance of anal HPV included douching, long-term tobacco smoking and anal sex.
Conclusions
The majority of anal HPV infections resolve in a relatively short time. Although anal HPV is commonly acquired in healthy women, its rapid clearance suggests limited efficacy of HPV testing as an anal cancer screening tool.
doi:10.1086/596758
PMCID: PMC2756215  PMID: 19191636
human papillomavirus; clearance; duration; cohort study; anal cancer
10.  Prevalence of human papillomavirus in university young women 
Oncology Letters  2011;2(4):701-706.
Cervical cancer is the second most prevalent female cancer worldwide. The majority of cases appear between the age of 30 and 50. Human papillomavirus (HPV) plays a central role in cervical cancer with 99.7% of HPV DNA identified in invasive cervical carcinomas. The prevalence of the HPV infection varies substantially among countries and according to age and lifestyle. HPV is a common sexually transmitted infection among males and females with a 70% higher incidence in sexually active females. This study aimed to determine the prevalence of human papillomavirus in young university women by analyzing the correlation between Papanicolaou (PAP)-stained cervical tests and HPV detection by genotyping, as well as other risk factors. A total of 200 women aged between 18 and 25 years were enrolled in this study, which took place between September 2008 and May 2009 at the Universidad de Tarapacá, Arica, Chile. Results of the PAP smears showed that 97.5% of cells had normal characteristics, although an inflammatory pattern was noted. The prevalence of generic HPV infection was 3.5% when testing for HPV DNA using the polymerase chain reaction (PCR) method. An analysis of the genotype of infected female individuals indicated that high-risk HPV types, such as HPV 16 and 31 were present in 42.84 and 14.29% of females, respectively, and low-risk types such as HPV 6, in 14.29%. Only one sample with differentiated non-HPV (14.29%) was found. A 95% correlation between PAP-stained cervical tests and the method of testing for HPV was observed. Using the PCR method, it was found that of the 195 negative PAP smears, 5 were positive for HPV and two of the samples that were positive for ASC-US were also positive. A significantly increased (P<0.05) HPV infection risk was observed in the 18–21 age group with a higher prevalence (71.40%) when compared to the 22–25 age group (28.6%). A significant (P<0.042) difference was found between smoking and HPV infection. In conclusion, a significant (P<0.05) correlation was found between PAP and PCR methods for HPV testing in young university women. A significant correlation between smoking and HPV was detected, whereas no difference was noted with other parameters.
doi:10.3892/ol.2011.290
PMCID: PMC3406457  PMID: 22848252
human papillomavirus; prevalence
11.  Decision-analytic modeling to evaluate the long-term effectiveness and cost-effectiveness of HPV-DNA testing in primary cervical cancer screening in Germany 
Background
Persistent infections with high-risk types of human papillomavirus (HPV) are associated with the development of cervical neoplasia. Compared to cytology HPV testing is more sensitive in detecting high-grade cervical cancer precursors, but with lower specificity. HPV based primary screening for cervical cancer is currently discussed in Germany. Decisions should be based on a systematic evaluation of the long-term effectiveness and cost-effectiveness of HPV based primary screening.
Research questions
What is the long-term clinical effectiveness (reduction in lifetime risk of cervical cancer and death due to cervical cancer, life years gained) of HPV testing and what is the cost-effectiveness in Euro per life year gained (LYG) of including HPV testing in primary cervical cancer screening in the German health care context? How can the screening program be improved with respect to test combination, age at start and end of screening and screening interval and which recommendations should be made for the German health care context?
Methods
A previously published and validated decision-analytic model for the German health care context was extended and adapted to the natural history of HPV infection and cervical cancer in order to evaluate different screening strategies that differ by screening interval, and tests, including cytology alone, HPV testing alone or in combination with cytology, and HPV testing with cytology triage for HPV-positive women. German clinical, epidemiological and economic data were used. In the absence of individual data, screening adherence was modelled independently from screening history. Test accuracy data were retrieved from international meta-analyses. Predicted outcomes included reduction in lifetime-risk for cervical cancer cases and deaths, life expectancy, lifetime costs, and discounted incremental cost-effectiveness ratios (ICER). The perspective of the third party payer and 3% annual discount rate were adopted. Extensive sensitivity analyses were performed in order to evaluate the robustness of results and identify areas of future research.
Results
In the base case analysis screening resulted in a 53% to 97% risk reduction for cervical cancer with a discounted ICER between 2,600 Euro/LYG (cytology alone every five years) and 155,500 Euro/LYG (Annual cytology age 20 to 29 years, and annual HPV age 30 years and older). Annual cytology, the current recommended screening strategy in Germany, was dominated. In sensitivity analyses variation in the relative increase in the sensitivity of HPV testing as compared to cytology, HPV test costs, screening adherence, HPV incidence, and annual discount rate influenced the ICER results. Variation in the screening start age also influenced the ICER. All cytology strategies were dominated by HPV screening strategies, when relative sensitivity increase by HPV testing compared to cytology was higher (scenario analysis with data for test accuracy from German studies). HPV testing every one, two or three years was more effective than annual cytology. With increased screening adherence a longer screening interval and with low screening adherence a shorter interval would be more cost-effective. With a reduction in HPV incidence of more than 70% triennial HPV screening in women aged 30 years and older (and biennial Pap screening in women aged 20 to 29 years) is cost-effective. The discounted ICER increases with increasing annual discount rate. Increasing screening start age to 25 years had no relevant loss in effectiveness but resulted in lower costs. An optimal strategy may be biennial HPV testing age 30 years and older with biennial cytology at age 25 to 29 years (ICER of 23,400 Euro/LYG).
Conclusions
Based on these results, HPV-based cervical cancer screening is more effective than cytology and could be cost-effective if performed at intervals of two years or greater. Increasing the age at screening start to 25 years causes no relevant loss in effectiveness but saves resources. In the German context an optimal screening strategy could be biennial HPV testing at age 30 years and older with biennial cytology at the age of 25 to 29 years. An extension to a three-yearly screening interval requires substantially improved screening adherence or a higher relative increase in the sensitivity of HPV testing as compared to cytology. The implementation of an organised screening program for quality-controlled introduction of HPV-screening and -vaccination with continued systematic outcome evaluation is recommended.
doi:10.3205/hta000083
PMCID: PMC3010885  PMID: 21289878
cervix; cervix of uterus; cervical carcinoma; carcinoma; cancer; cytology; human papillomavirus; HPV; DNA; HPV-DNA diagnosis; diagnosis; early finding; screening; primary screening; test; decision-analytical modelling; Markov model; effectiveness; systematic review; meta-analysis; Health Technology Assessment; long-term effectiveness; cost-effectiveness; health economic evaluation
12.  Epidemiological Study of Anti-HPV16/18 Seropositivity and Subsequent Risk of HPV16 and -18 Infections 
Background
Infection with human papillomavirus (HPV) 16 or HPV18 elicits an antibody response, but whether the elicited antibodies protect women against subsequent infection by a homologous HPV type compared with seronegative women is unknown.
Methods
Study participants were women aged 18–25 years at enrollment in the control group of the ongoing National Cancer Institute–sponsored, community-based, randomized HPV16/18 Costa Rica Vaccine Trial. At enrollment, 2813 participants were negative for cervical HPV16 DNA and 2950 for HPV18 DNA. Women were interviewed regarding sociodemographic data and medical and health history. Medical and pelvic examinations were conducted for all consenting sexually experienced women. Serum samples taken at enrollment were tested for total HPV16/18 antibodies with a polyclonal enzyme-linked immunosorbent assay, and cervical specimens were tested for type-specific HPV DNA over 4 years of follow-up. Using Poisson regression, we compared rate ratios of newly detected cervical HPV16 or HPV18 infection among homologous HPV-seropositive and HPV-seronegative women, adjusting for age, education, marital status, lifetime number of sexual partners, and smoking.
Results
There were 231 newly detected HPV16 infections during 5886 person-years among HPV16-seronegative women compared with 12 newly detected HPV16 infections during 581 person-years among HPV16-seropositive women with the highest HPV16 sero-levels. There were 136 newly detected HPV18 infections during 6352 person-years among HPV18-seronegative women compared with six new infections detected during 675 person-years among HPV18 seropositives with the highest sero-levels. After controlling for risk factors associated with newly detected HPV infection, having high HPV16 antibody titer at enrollment was associated with a reduced risk of subsequent HPV16 infection (women in the highest tertile of HPV16 antibody titers, adjusted rate ratio = 0.50, 95% confidence interval = 0.26 to 0.86 vs HPV16-seronegative women). Similarly, having high HPV18 antibody titer at enrollment was associated with a reduced risk of subsequent HPV18 infection (women in the highest tertile of HPV18 antibody titers, adjusted rate ratio = 0.36, 95% confidence interval = 0.14 to 0.76 vs HPV18-seronegative women).
Conclusion
In this study population, having high antibody levels against HPV16 and HPV18 following natural infection was associated with reduced risk of subsequent HPV16 and HPV18 infections.
doi:10.1093/jnci/djq384
PMCID: PMC2970577  PMID: 20944077
13.  The Relationship between Cocaine Use and Human Papillomavirus Infections in HIV-Seropositive and HIV-Seronegative Women 
Objective. Animal data suggest that cocaine has an immunosuppressive effect, but no human studies have been conducted to assess the relation of cocaine use with human papillomavirus (HPV) infection, the viral cause of cervical cancer. Since both cocaine use and HPV infection are common among HIV-positive women, we sought to determine whether use of cocaine and/or crack influences the natural history of HPV among women with or at high risk of HIV. Methods. Women enrolled in the Women's Interagency HIV Study (2278 HIV-seropositive and 826 high-risk seronegative women) were examined every six months for up to 9.5 years with Pap smear, collection of cervicovaginal lavage (CVL) samples, and detailed questionnaires regarding health and behavior, including use of crack and cocaine (crack/cocaine). CVLs were tested for HPV DNA by PCR, with genotyping for over forty HPV types. Results. In multivariate logistic regression models, censoring women treated for cervical neoplasia, crack/cocaine use within the last six months was associated with prevalent detection of oncogenic HPV DNA (odds ratio [OR] = 1.30 (1.09–1.55)), and with oncogenic HPV-positive squamous intraepithelial lesions (SIL) (OR = 1.70 (1.27–2.27)), following adjustment for age, race, HIV-serostatus, and CD4+ T-cell count, the number of sexual partners in the past six months, and smoking. In multivariate Cox models crack/cocaine use was also associated with a trend that approached significance in regard to incident detection of oncogenic HPV-positive SIL (HR = 1.51, 95% CI 0.99–2.30), and while the rate of oncogenic HPV clearance was not related to cocaine use, the clearance of any SIL was significantly lower in those with versus those without recent crack/cocaine use (HR = 0.57, 95% CI 0.34–0.97). Conclusions. Cocaine use is associated with an increased risk of detection of both prevalent and incident oncogenic HPV infection, as well as an increased risk of HPV-positive SIL over time.
doi:10.1155/2008/587082
PMCID: PMC2324195  PMID: 18437233
14.  Type-specific incidence, clearance and predictors of cervical human papillomavirus infections (HPV) among young women: a prospective study in Uganda 
Background
While infections with human papillomavirus (HPV) are highly prevalent among sexually active young women in Uganda, information on incidence, clearance and their associated risk factors is sparse. To estimate the incidence, prevalence and determinants of HPV infections, we conducted a prospective follow-up study among 1,275 women aged 12-24 years at the time of recruitment. Women answered a questionnaire and underwent a pelvic examination at each visit to collect exfoliated cervical cells. The presence of 42 HPV types was evaluated in exfoliated cervical cells by a polymerase chain based (PCR) assay (SPF10-DEIA LiPA).
Results
Three hundred and eighty (380) of 1,275 (29.8%) women were followed up for a median time of 18.5 months (inter-quartile range 9.7-26.6). Sixty-nine (69) women had incident HPV infections during 226 person-years of follow-up reflecting an incidence rate of 30.5 per 100 person-years. Incident HPV infections were marginally associated with HIV positivity (RR = 2.8, 95% CI: 0.9 - 8.3). Clearance for HPV type-specific infections was frequent ranging between 42.3% and 100.0% for high- and 50% and 100% for low-risk types. Only 31.2% of women cleared all their infections. Clearance was associated with HIV negativity (Adjusted clearance = 0.2, 95% CI: 0.1 - 0.7) but not with age at study entry, lifetime number of sexual partners and multiplicity of infections. The prevalence of low-grade squamous intraepithelial lesions (LSILs) was 53/365 (14.5%). None of the women had a high-grade cervical lesion (HSIL) or cancer. Twenty-two (22) of 150 (14.7%) HPV negative women at baseline developed incident LSIL during follow-up. The risk for LSIL appeared to be elevated among women with HPV 18-related types compared to women not infected with those types (RR = 3.5, 95% CI: 1.0 - 11.8).
Conclusions
Incident HPV infections and type-specific HPV clearance were frequent among our study population of young women. These results underscore the need to vaccinate pre-adolescent girls before initiation of sexual activity.
doi:10.1186/1750-9378-5-7
PMCID: PMC2873244  PMID: 20380709
15.  Association of HIV infection with distribution and viral load of HPV types in Kenya: a survey with 820 female sex workers 
Background
Human papillomavirus (HPV) and HIV are each responsible for a considerable burden of disease. Interactions between these infections pose substantial public health challenges, especially where HIV prevalence is high and HPV vaccine coverage low.
Methods
Between July 2005 and January 2006, a cross-sectional community-based survey in Mombasa, Kenya, enrolled female sex workers using snowball sampling. After interview and a gynaecological examination, blood and cervical cytology samples were taken. Quantitative real-time PCR detected HPV types and viral load measures. Prevalence of high-risk HPV was compared between HIV-infected and -uninfected women, and in women with abnormal cervical cytology, measured using conventional Pap smears.
Results
Median age of the 820 participants was 28 years (inter-quartile range [IQR] = 24-36 years). One third of women were HIV infected (283/803; 35.2%) and these women were y more likely to have abnormal cervical cytology than HIV-negative women (27%, 73/269, versus 8%, 42/503; P < 0.001). Of HIV-infected women, 73.3% had high-risk HPV (200/273) and 35.5% had HPV 16 and/or 18 (97/273). Corresponding figures for HIV-negative women were 45.5% (229/503) and 15.7% (79/503). After adjusting for age, number of children and condom use, high-risk HPV was 3.6 fold more common in HIV-infected women (95%CI = 2.6-5.1). Prevalence of all 15 of the high-risk HPV types measured was higher among HIV-infected women, between 1.4 and 5.5 fold. Median total HPV viral load was 881 copies/cell in HIV-infected women (IQR = 33-12,110 copies/cell) and 48 copies/cell in HIV-uninfected women (IQR = 6-756 copies/cell; P < 0.001). HPV 16 and/or HPV 18 were identified in 42.7% of LSIL (32/75) and 42.3% of HSIL (11/26) lesions (P = 0.98). High-risk HPV types other than 16 and 18 were common in LSIL (74.7%; 56/75) and HSIL (84.6%; 22/26); even higher among HIV-infected women.
Conclusions
HIV-infected sex workers had almost four-fold higher prevalence of high-risk HPV, raised viral load and more precancerous lesions. HPV 16 and HPV 18, preventable with current vaccines, were associated with cervical disease, though other high-risk types were commoner. HIV-infected sex workers likely contribute disproportionately to HPV transmission dynamics in the general population. Current efforts to prevent HIV and HPV are inadequate. New interventions are required and improved implementation of existing strategies.
doi:10.1186/1471-2334-10-18
PMCID: PMC2845133  PMID: 20102630
16.  Frequency and risk factors for prevalent, incident, and persistent genital carcinogenic human papillomavirus infection in sexually active women: community based cohort study 
Objective To investigate frequency and risk factors for prevalent, incident, and persistent carcinogenic human papillomavirus (HPV) in young women before the introduction of immunisation against HPV types 16 and 18 for schoolgirls.
Design Cohort study
Setting 20 London universities and further education colleges.
Participants 2185 sexually active female students, mean age 21 years (range 16-27), 38% from ethnic minorities, who took part in the POPI (prevention of pelvic infection) chlamydia screening trial in 2004-08 and who provided duplicate, self taken vaginal swabs and completed questionnaires at baseline. At follow-up, a median of 16 months later, 821 women (38%) returned repeat vaginal swabs by post. In 2009-10, stored samples were tested for HPV.
Results Samples from 404/2185 (18.5% (95% CI 16.9% to 20.2%)) of the cohort were positive for carcinogenic HPV at baseline, including 15.0% (327) positive for non-vaccine carcinogenic genotypes. Reporting two or more sexual partners in the previous year and concurrent Chlamydia trachomatis or bacterial vaginosis were independent risk factors for prevalent vaginal HPV infection. Infection with one or more new HPV types was found in 17.7% (145/821) of follow-up samples, giving an estimated annual incidence of carcinogenic HPV infection of 12.9% (95% CI 11.0% to 15.0%). Incident infection was more common in women reporting two or more partners in the previous year, aged<20, of black ethnicity, or with C trachomatis vaginosis at baseline. Multiple partners was the only independent risk factor for incident infection (adjusted relative risk 1.99 (95% CI 1.46 to 2.72)). Of 143 women with baseline carcinogenic HPV infection, 20 (14% (8.3% to 19.7%) had infection with the same carcinogenic HPV type(s) detected after 12-28 months. Of these women, 13 (65%) had redetected infection with HPV 16 or 18, and nine (45%) with non-vaccine carcinogenic HPV genotypes.
Conclusion In the first UK cohort study of carcinogenic HPV in young women in the community, multiple sexual partners was an independent predictor of both prevalent and incident infection. Infection with non-vaccine carcinogenic genotypes was common. Although current HPV vaccines offer partial cross protection against some non-vaccine carcinogenic HPV types, immunised women will still need cervical screening.
doi:10.1136/bmj.e4168
PMCID: PMC3382227  PMID: 22730542
17.  Prevalence and type distribution of human papillomavirus infection in women from North Sardinia, Italy 
BMC Public Health  2011;11:785.
Background
Human papillomavirus (HPV) has been associated with several disorders of the genital tract, skin and oropharynx. The aims of our study were to evaluate the prevalence of HPV infection in women between 15 and 54 years of age in North Sardinia, Italy, to identify the prevalence of High Risk - Human papillomaviruses (HR-HPV) genotypes and to establish a correlation between molecular and cytological results.
Methods
From 2007 to 2009 we consecutively enrolled women aged 15-54 years admitted to public and private outpatient settings. All the participants filled in a questionnaire about the socio-cultural state, sexual activity and awareness about HPV. 323 cervical specimens were tested for HPV-DNA and HPV genotypes with INNO-LiPA HPV Genotyping CE Amp kit. Samples showing positivity to some HPV genotypes were re-tested using "in house" quantitative Real-Time PCR assays.
Results
Overall HPV-DNA positivity was detected in 35.9% of the women. The prevalence of HR-HPV infection among HPV positive samples was 93.1% with a specific prevalence of HPV 16, 51, 31, 53 and 18 of 54.3%, 37.9%, 10.3%, 6.9% and 5.2%, respectively. Co-infection with any HPV, HR-HPV, LR-HPV and HR/LR-HPV type was 18.3%, 14.9%, 0.9% and 2.5%, respectively; HPV 16/51 co-infection was detected in 64.6% of the HR-HPV co-infection group. The most frequent HPV-genotypes detected were 16 (32.5%) and 51 (22.7%). Among the 57 patients harboring mono-infection the most prevalent HPV genotypes were 16 (38.6%) and 31(10.5%). A multivariate analysis identified a statistical significant association between HPV infection and age and between HPV infection and previous sexual transmitted diseases. A statistically significant association between cytological cervical lesions and generic HPV exposure was identified.
Conclusions
To our knowledge, this is the first survey evaluating the prevalence of HPV infection in Northern Sardinia and drawing attention to the unusual high proportion of genotype HPV 51. Given the recent implementation of a widespread immunization program with vaccines not containing HPV 51, it has been relevant to prove the high prevalence of this HPV genotype from the start of the vaccination campaign, in order to avoid in the future attributing to the vaccination program a possible selection effect (HPV replacement).
doi:10.1186/1471-2458-11-785
PMCID: PMC3208589  PMID: 21989375
18.  The distribution of sexually-transmitted Human Papillomaviruses in HIV positive and negative patients in Zambia, Africa 
Background
Human Papillomaviruses (HPV) are double-stranded DNA viruses, considered to be the primary etiological agents in cervical intraepithelial neoplasias and cancers. Approximately 15–20 of the 40 mucosal HPVs confer a high-risk of progression of lesions to invasive cancer. In this study, we investigated the prevalence of sexually transmitted HPVs in Human Immunodeficiency Virus (HIV) positive and negative patients in Zambia, Africa. The rate of high-risk HPV genotypes worldwide varies within each country. Thus, we sought to investigate the rates of HPV infection in sub-Saharan Africa and the potential role of HIV in affecting the HPV genotype distribution.
Methods
This retrospective cross-sectional study reports findings on the association and effects of HIV on HPV infections in an existing cohort of patients at University Teaching Hospital (UTH) Lusaka, Zambia. The objective of this study was to assess HPV prevalence, genotype distribution and to identify co-factors that influence HPV infection. Polymerase chain reaction (PCR) with two standard consensus primer sets (CpI/II and GP5+/6+) was used to test for the presence of HPV DNA. Primers specific for β-actin were used to monitor DNA quality. Vaginal lavage samples, collected between 1998-1999 from a total of 70 women, were part of a larger cohort that was also analyzed for HIV and human herpesvirus infection. Seventy of the samples yielded usable DNA. HIV status was determined by two rapid assays, Capillus and Determine. The incidence of HIV and HPV infections and HPV genotype distributions were calculated and statistical significance was determined by Chi-Squared test.
Results
We determined that most common HPV genotypes detected among these Zambian patients were types 16 and 18 (21.6% each), which is approximately three-fold greater than the rates for HPV16, and ten-fold greater than the rates for HPV18 in the United States. The worldwide prevalence of HPV16 is approximately 14% and HPV18 is 5%. The overall ratio of high-risk (HR) to low-risk (LR) HPVs in the patient cohort was 69% and 31% respectively; essentially identical to that for the HR and LR distributions worldwide. However, we discovered that HIV positive patients were two-times as likely to have an HR HPV as HIV negative individuals, while the distribution of LR HPVs was unaffected by HIV status. Interestingly, we observed a nine-fold increase in HPV18 infection frequency in HIV positive versus HIV negative individuals.
Conclusion
The rate of oncogenic HPVs (type 16 and 18) in Zambia was much higher than in the U.S., potentially providing an explanation for the high-rates of cervical cancer in Zambia. Surprisingly, we discovered a strong association between positive HIV status and the prevalence of HR HPVs, and specifically HPV18.
doi:10.1186/1471-2334-7-77
PMCID: PMC1949816  PMID: 17634108
19.  Significance of HPV-58 Infection in Women Who Are HPV-Positive, Cytology-Negative and Living in a Country with a High Prevalence of HPV-58 Infection 
PLoS ONE  2013;8(3):e58678.
Purpose
Cervical cytology and human papillomavirus (HPV) DNA co-testing is recommended as a screening method for detecting cervical lesions. However, for women who are HPV-positive but cytology-negative, the appropriate management and significance of HPV-58 infection remain unknown.
Methods
This study of prevalent HPV detected at baseline with a median follow-up of 3.2 years evaluated the risk factors associated with cervical abnormalities and assessed the significance of HPV-58 infection. A total of 265 women were enrolled. All high-grade squamous intraepithelial lesions (HSIL) that were detected by cytology were confirmed by histology. Histological diagnoses of cervical intraepithelial neoplasia 2/3 were classified as HSIL. Women were classified into four groups according to the HPV genotype that was detected at their first visit: HPV-58 (n = 27), HPV-16 (n = 52; 3 women had HPV-58 co-infection), ten other high risk (HR) types (n = 79), or low/undetermined risk types (n = 107).
Results
Of 265 women, 20 (7.5%) had HSIL on their follow-up examinations. There were significant differences in the cumulative incidence of HSIL between the four groups (p<0.001). The 5-year cumulative incidence rates of HSIL were 34.0% (95% CI: 17.3–59.8%) in HPV-58 positive cases, 28.0% (95% CI: 13.8–51.6) in HPV-16 positive cases, 5.5% (95% CI: 2.1–14.0%) in one of the ten other types of HR-HPV positive cases, and 0% in women with low/undetermined risk HPV. When seen in women with HR-HPV (n = 158), persistent HPV infection was a significant factor associated with the development of HSIL (hazard ratio = 15.459, 95% CI: 2.042–117.045). Women with HPV-58 had a higher risk (hazard ratio = 5.260, 95% CI: 1.538–17.987) for the development of HSIL than women with HPV-16 (hazard ratio = 3.822, 95% CI: 1.176–12.424) in comparison with women with other types of HR-HPV.
Conclusion
HPV-58 has a high association with the development of HSIL in women who are HPV-positive and cytology-negative.
doi:10.1371/journal.pone.0058678
PMCID: PMC3591398  PMID: 23505548
20.  Short-time repeat high-risk HPV testing by self-sampling for screening of cervical cancer 
British Journal of Cancer  2011;105(5):694-697.
Background:
Testing for high-risk human papillomavirus (HPV) in primary screening for cervical cancer is considered more sensitive, but less specific, in comparison with Pap-smear cytology. Women with persistent HPV infections have a higher risk of developing cervical intraepithelial neoplasia 2+ (CIN2+) lesions. This study was performed to evaluate the gain in specificity for detection of histologically confirmed CIN2+ lesions achieved by short-time repeat testing for high-risk HPV in women aged 30–65 years, with the primary sample for HPV analysis taken by self-sampling.
Methods:
A total of 8000 women in Uppsala County, aged 30–65 years, who had not attended organised screening for 6 years or longer, were offered self-sampling of vaginal fluid at home and the samples sent for HPV typing. Of these, 8% (669) were not possible to contact or had performed hysterectomy. Women positive for high-risk HPV in the self-sampling test were invited for a follow-up HPV test and a cervical biopsy on average 3 months after the initial HPV test.
Results:
In all, 39% (2850/7331) of invited women chose to perform self-sampling of vaginal fluid at home. High-risk HPV infection was found in 6.6% (188) of the women. In all, 89% of the women testing HPV positive performed a follow-up examination, on average 2.7 months, after the first test and 59% of these women were HPV positive in the follow-up test. The prevalence of CIN2+ lesions in women with an initial HPV-positive test was 23% (95% CI 18–30%) and in women with two consecutive HPV-positive tests was 41% (95% CI 31–51%). In women with two positive HPV tests, the prevalence of CIN2+ lesions varied from 49% in women at age 30–39 years to 24% in women at age 50–65 years. Short-time repeat HPV testing increased the specificity for detection of CIN2+ lesions from about 94.2% to 97.8%. The most prevalent HPV types were HPV16 (32%), followed by HPV18/45 (19%) and HPV 33/52/58 (19%).
Conclusion:
The short-time persistence of high-risk HPV infection in this age group was about 60%. Repeat testing for high-risk HPV using self-sampling of vaginal fluid can be used to increase the specificity in the screening for cervical cancer in women aged 30–65 years.
doi:10.1038/bjc.2011.277
PMCID: PMC3188941  PMID: 21811250
cervix; screening; carcinoma; HPV test; persistence; self-sampling
21.  Interventions for encouraging sexual behaviours intended to prevent cervical cancer 
Background
Human papillomavirus (HPV) is the key risk factor for cervical cancer. Continuing high rates of HPV and other sexually transmitted infections (STIs) in young people demonstrate the need for effective behavioural interventions.
Objectives
To assess the effectiveness of behavioural interventions for young women to encourage safer sexual behaviours to prevent transmission of STIs (including HPV) and cervical cancer.
Search methods
Systematic literature searches were performed on the following databases: Cochrane Central Register of Controlled Trials (CENTRAL Issue 4, 2009) Cochrane Gynaecological Cancer Review Group (CGCRG) Specialised Register, MEDLINE, EMBASE, CINAHL, PsychINFO, Social Science Citation Index and Trials Register of Promoting Health Interventions (TRoPHI) up to the end of 2009. All references were screened for inclusion against selection criteria.
Selection criteria
Randomised controlled trials (RCTs) of behavioural interventions for young women up to the age of 25 years that included, amongst other things, information provision about the transmission and prevention of STIs. Trials had to measure behavioural outcomes (e.g. condom use) and/or biological outcomes (e.g. incidence of STIs, cervical cancer).
Data collection and analysis
A narrative synthesis was conducted. Meta-analysis was not considered appropriate due to heterogeneity between the interventions and trial populations.
Main results
A total of 5271 references were screened and of these 23 RCTs met the inclusion criteria. Most were conducted in the USA and in health-care clinics (e.g. family planning).
The majority of interventions provided information about STIs and taught safer sex skills (e.g. communication), occasionally supplemented with provision of resources (e.g. free sexual health services). They were heterogeneous in duration, contact time, provider, behavioural aims and outcomes. A variety of STIs were addressed including HIV and chlamydia. None of the trials explicitly mentioned HPV or cervical cancer prevention.
Statistically significant effects for behavioural outcomes (e.g. increasing condom use) were common, though not universal and varied according to the type of outcome. There were no statistically significant effects of abstaining from or reducing sexual activity. There were few statistically significant effects on biological (STI) outcomes. Considerable uncertainty exists in the risk of bias due to incomplete or ambiguous reporting.
Authors’ conclusions
Behavioural interventions for young women which aim to promote sexual behaviours protective of STI transmission can be effective, primarily at encouraging condom use. Future evaluations should include a greater focus on HPV and its link to cervical cancer, with long-term follow-up to assess impact on behaviour change, rates of HPV infection and progression to cervical cancer. Studies should use an RCT design where possible with integral process evaluation and cost-effectiveness analysis where appropriate. Given the predominance of USA studies in this systematic review evaluations conducted in other countries would be particularly useful.
doi:10.1002/14651858.CD001035.pub2
PMCID: PMC4040418  PMID: 21491379
*Safe Sex; Condoms [utilization]; Randomized Controlled Trials as Topic; Sexual Behavior; Sexually Transmitted Diseases [*prevention & control]; Uterine Cervical Neoplasms [*prevention & control]; Adolescent; Female; Humans; Young Adult
22.  Low risk of type-specific carcinogenic HPV re-appearance with subsequent cervical intraepithelial neoplasia grade 2/3 
Carcinogenic human papillomavirus (HPV) infections are very common after sexual debut and nearly all become undetectable (“clear”) within a few years. Following clearance, the long-term risks of type-specific HPV re-appearance and subsequent risk of cervical intraepithelial neoplasia grade 2 or worse (CIN2+) are not well defined.
In the 7-year, population-based cohort study in Guanacaste, Costa Rica, we studied how often type-specific carcinogenic HPV infections re-appeared after clearance, and how often re-appearance led to CIN2+. We considered 1740 carcinogenic HPV infections detected by MY09/11 PCR among 2805 women (18-91 years old, median 34) who were actively followed at 6- or 12-month intervals. We identified women with 1 or more type-specific HPV infections that cleared and re-appeared, and further defined a subgroup of “definite clearance and re-appearance” (≥ 2 intervening negative results over a period of ≥ 1 year). We determined the absolute risk of CIN2+ among the different groups. P values are two sided.
Only 7.7% (81/1052) of HPV-infected women had intervening negative results. Very few (3.7%, 39/1052) had “definite clearance and re-appearance”, of which 5.1% (2/39) subsequently persisted to a diagnosis of CIN2. There were zero CIN3+ lesions.
Extremely few women (2/2805 of women in our cohort) had a type-specific carcinogenic HPV infection clear, re-appear and lead to CIN2+. If confirmed, this argues against vaccination to avoid re-appearance that leads to precursor lesions and against the need of frequent HPV screening after initial negative results.
doi:10.1002/ijc.27418
PMCID: PMC3356792  PMID: 22213126
HPV infection re-appearance; CIN2+ risk after re-appearance; HPV infection epidemiology
23.  Type-Specific Cervico-Vaginal Human Papillomavirus Infection Increases Risk of HIV Acquisition Independent of Other Sexually Transmitted Infections 
PLoS ONE  2010;5(4):e10094.
Background
Sexually transmitted infections (STIs) such as herpes simplex virus (HSV)-2 are associated with an increased risk of HIV infection. Human papillomavirus (HPV) is a common STI, but little is know about its role in HIV transmission. The objective of this study was to determine whether cervico-vaginal HPV infection increases the risk of HIV acquisition in women independent of other common STIs.
Methods and Findings
This prospective cohort study followed 2040 HIV-negative Zimbabwean women (average age 27 years, range 18–49 years) for a median of 21 months. Participants were tested quarterly for 29 HPV types (with L1 PCR primers) and HIV (antibody testing on blood samples with DNA or RNA PCR confirmation). HIV incidence was 2.7 per 100 woman-years. Baseline HPV prevalence was 24.5%, and the most prevalent HPV types were 58 (5.0%), 16 (4.7%), 70 (2.4%), and 18 (2.3%). In separate regression models adjusting for baseline variables (including age, high risk partner, positive test for STIs, positive HSV-2 serology and condom use), HIV acquisition was associated with having baseline prevalent infection with HPV 58 (aHR 2.13; 95% CI 1.09–4.15) or HPV 70 (aHR 2.68; 95% CI 1.08–6.66). In separate regression models adjusting for both baseline variables and time-dependent variables (including HSV-2 status, incident STIs, new sexual partner and condom use), HIV acquisition was associated with concurrent infection with any non-oncogenic HPV type (aHR 1.70; 95% CI 1.02–2.85), any oncogenic HPV type (aHR 1.96; 95% CI 1.16–3.30), HPV 31 (aHR 4.25; 95% CI 1.81–9.97) or HPV 70 (aHR 3.30; 95% CI 1.50–7.20). Detection of any oncogenic HPV type within the previous 6 months was an independent predictor of HIV acquisition, regardless of whether HPV status at the HIV acquisition visit was included (aHR 1.95; 95% CI 1.19–3.21) or excluded (aHR 1.96; 95% CI 1.02–2.85) from the analysis.
Conclusions/Significance
Cervico-vaginal HPV infection was associated with an increased risk of HIV acquisition in women, and specific HPV types were implicated in this association. The observational nature of our study precludes establishment of causation between HPV infection and HIV acquisition. However, given the high prevalence of HPV infection in women, further investigation of the role of HPV in HIV transmission is warranted.
doi:10.1371/journal.pone.0010094
PMCID: PMC2851652  PMID: 20386706
24.  253 Use of Transfer Factor in Patients with Persistent Genital Human Papillomavirus Infection 
Background
Human papillomavirus (HPV) is the most common sexually transmitted infection worldwide. About 75 to 80% of sexually active Americans will be infected with HPV at some point in their lifetime. The risk of HPV infection seems to be related with age at first intercourse, younger age and number of sexual partners. HPV infection is limited to the basal cells of stratified epithelium of the skin or mucous membranas. There is a wide latency period, from months to years, before squamous intraepithelial lesions develop. Most HPV infections are cleared within 2 years by the immune system. Only in 5% to 10% of infected women with “high risk” types the infection persists determining a high risk of developing intraepithelial neoplasias, as cervical cancer, vulvar cancer, penile cancer, and/or anal cancer. The gynecological evaluation and Papanicolau smear are the primary screening tools for detecting HPV infection. There is currently no specific treatment for HPV infection. The Transfer Factor (TF) or Dialyzable Leukocyte Extract is an immunomodulator that has been successfully used as an adjuvant in the treatment of intracelular infections such as recurrent herpes virus diseases. TF induces the expression of RNAm and IFN-γ and increases CD4+ cells. The IFN-γ activates macrophages, neutrophils, B lymphocytes, NK cells, and favours the differentiation of T cells into Th1 lymphocytes that are requiried for the control of intracellular patho gens.
Methods
We used TF in a group of patients with persistent genital human papillomavirus infection.
Results
We included 12 patients, aged 19 to 45 years old (mean 30), with 14 to 23 years at first intercourse and a mean of 3 sexual partners in their lifetime. All of them had persistent HPV that had been treated before with local and ablative therapeutic options (including cervical freezing, cauterizing loop, imiquimod, podophyllin and/or cervical conization). Transfer factor was administered daily for 5 days, and subsequently at 7-day intervals for 5 weeks. We found an important improvement in the gynecological evaluation of cervix and perineal lesions and a significant reduction in the frequency of relapses.
Conclusions
Transfer factor could be used as an adjuvant in patients with persistent genital human papillomavirus infection.
doi:10.1097/01.WOX.0000412010.68985.28
PMCID: PMC3513045
25.  The interrelation of HIV, cervical human papillomavirus, and neoplasia among antenatal clinic attenders in Tanzania 
Sexually Transmitted Infections  2001;77(4):248-254.
* Died April 2000
Objectives: To determine the prevalence and interrelation of cervical human papillomavirus (HPV) genotypes, squamous intraepithelial lesions (SIL), HIV, and other reproductive tract infections (RTIs) among urban antenatal clinic attenders in Mwanza, Tanzania.
Methods: Genital swabs were collected from 660 pregnant women and tested for a range of RTIs and for cervical cytology. Cervical HPV-DNA was detected by PCR and genotyped. HIV and syphilis serologies were performed.
Results: HPV prevalence was 34% (209/612 women). Of the 144 typeable samples, 83% were high risk (HR-HPV) oncogenic strains (56% HPV 16 related types). SIL was detected in 43 women (7%), with high grade SIL in 3%. There was a high prevalence of HIV (15%), and of any RTI (83%). Genital warts were detected in 20 women (3%). HPV infection was associated with some behavioural factors (short duration of relationship, single status, not using condoms) and gonorrhoea. There was no overall association between HPV and HIV (OR=1.02, 95% CI 0.6–1.6), but a non-significant trend towards a stronger association with HR-HPV in women aged 15–19 (OR=2.79, 95% CI 0.8–9.5) and women aged ≥30 (OR=3.20, 95% CI 0.7–15). SIL was associated with HPV (OR=3.66, 95% CI 1.9–7.0), but not significantly with HIV (OR=1.54, 95% CI 0.7–3.4). Prevalence of SIL was higher among women dually positive for HPV/HIV compared to HPV infection only (21% v 12%), although this difference was not statistically significant (p=0.17).
Conclusions: HPV infection was highly prevalent in this young antenatal population. The association of HIV with HR-HPV types in older women may suggest that the principal HIV/HPV interaction in this population is for HIV to upregulate HPV persistence, leading to subsequent development of SIL.
Key Words: human papillomavirus; squamous intraepithelial lesion; HIV/AIDS; Africa
doi:10.1136/sti.77.4.248
PMCID: PMC1744347  PMID: 11463923

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