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1.  Validity of Parent-Reported Vaccination Status for Adolescents Aged 13–17 Years: National Immunization Survey-Teen, 2008 
Public Health Reports  2011;126(Suppl 2):60-69.
The validity of parent-reported adolescent vaccination histories has not been assessed. This study evaluated the validity of parent-reported adolescent vaccination histories by a combination of immunization card and recall, and by recall only, compared with medical provider records.
We analyzed data from the 2008 National Immunization Survey-Teen. Parents of adolescents aged 13–17 years reported their child's vaccination history either by immunization card and recall (n=3,661) or by recall only (n=12,822) for the hepatitis B (Hep B), measles-mumps-rubella (MMR), varicella (VAR), tetanus-diphtheria/tetanus-diphtheria-acellular pertussis (Td/Tdap), meningococcal conjugate (MCV4), and quadrivalent human papillomavirus (HPV4) (for girls only) vaccines. We validated parental report with medical records.
Among the immunization card/recall group, vaccines with >20% false-positive reports included MMR (32.3%) and Td/Tdap (36.9%); vaccines with >20% false-negative reports included VAR (35.2%), MCV4 (36.0%), and Tdap (41.9%). Net bias ranged from −25.0 to −0.1 percentage points. Kappa values ranged from 0.22 to 0.92. Among the recall-only group, vaccines with >20% false-positive reports included Hep B (33.9%), MMR (61.4%), VAR (26.2%), and Td/Tdap (60.6%); vaccines with >20% false-negative reports included Hep B (58.9%), MMR (33.7%), VAR (51.6%), Td/Tdap (25.5%), Tdap (50.3%) MCV4 (63.0%), and HPV4 (20.5%). Net bias ranged from −46.0 to 0.5 percentage points. Kappa values ranged from 0.03 to 0.76.
Validity of parent-reported vaccination histories varies by type of report and vaccine. For recently recommended vaccines, false-negative rates were substantial and higher than false-positive rates, resulting in net underreporting of vaccination rates by both the immunization card/recall and recall-only groups. Provider validation of parent-reported vaccinations is needed for valid surveillance of adolescent vaccination coverage.
PMCID: PMC3113431  PMID: 21812170
2.  Measles vaccination coverage estimates from surveys, clinic records, and immune markers in oral fluid and blood: a population-based cross-sectional study 
BMC Public Health  2013;13:1211.
Recent outbreaks of measles and polio in low-income countries illustrate that conventional methods for estimating vaccination coverage do not adequately identify susceptible children. Immune markers of protection against vaccine-preventable diseases in oral fluid (OF) or blood may generate more accurate measures of effective vaccination history, but questions remain about whether antibody surveys are feasible and informative tools for monitoring immunization program performance compared to conventional vaccination coverage indicators. This study compares six indicators of measles vaccination status, including immune markers in oral fluid and blood, from children in rural Bangladesh and evaluates the implications of using each indicator to estimate measles vaccination coverage.
A cross-sectional population-based study of children ages 12–16 months in Mirzapur, Bangladesh, ascertained measles vaccination (MCV1) history from conventional indicators: maternal report, vaccination card records, ‘card + history’ and EPI clinic records. Oral fluid from all participants (n = 1226) and blood from a subset (n = 342) were tested for measles IgG antibodies as indicators of MCV1 history and compared to conventional MCV1 coverage indicators.
Maternal report yielded the highest MCV1 coverage estimates (90.8%), followed by EPI records (88.6%), and card + history (84.2%). Seroprotection against measles by OF (57.3%) was significantly lower than other indicators, even after adjusting for incomplete seroconversion and assay performance (71.5%). Among children with blood results, 88.6% were seroprotected, which was significantly higher than coverage by card + history and OF serostatus but consistent with coverage by maternal report and EPI records. Children with vaccination cards or EPI records were more likely to have a history of receiving MCV1 than those without cards or records. Despite similar MCV1 coverage estimates across most indicators, within-child agreement was poor for all indicators.
Measles IgG antibodies in OF was not a suitable immune marker for monitoring measles vaccination coverage in this setting. Because agreement between conventional MCV1 indicators was mediocre, immune marker surveillance with blood samples could be used to validate conventional MCV1 indicators and generate adjusted results that can be compared across indicators.
PMCID: PMC3890518  PMID: 24359402
Immunization; Vaccination; Immune marker; Surveillance; Measles; Oral fluid; Vaccination card; Maternal report; Bangladesh
3.  Vaccine coverage and determinants of incomplete vaccination in children aged 12–23 months in Dschang, West Region, Cameroon: a cross-sectional survey during a polio outbreak 
BMC Public Health  2015;15:630.
Inadequate immunization coverage with increased risk of vaccine preventable diseases outbreaks remains a problem in Africa. Moreover, different factors contribute to incomplete vaccination status. This study was performed in Dschang (West Region, Cameroon), during the polio outbreak occurred in October 2013, in order to estimate the immunization coverage among children aged 12–23 months, to identify determinants for incomplete vaccination status and to assess the risk of poliovirus spread in the study population.
A cross-sectional household survey was conducted in November-December 2013, using the WHO two-stage sampling design. An interviewer-administered questionnaire was used to obtain information from consenting parents of children aged 12–23 months. Vaccination coverage was assessed by vaccination card and parents’ recall. Chi-square test and multilevel logistic regression model were used to identify the determinants of incomplete immunization status. Statistical significance was set at p < 0.05.
Overall, 3248 households were visited and 502 children were enrolled. Complete immunization coverage was 85.9 % and 84.5 %, according to card plus parents’ recall and card only, respectively. All children had received at least one routine vaccination, the OPV-3 (Oral Polio Vaccine) coverage was >90 %, and 73.4 % children completed the recommended vaccinations before 1-year of age. In the final multilevel logistic regression model, factors significantly associated with incomplete immunization status were: retention of immunization card (AOR: 7.89; 95 % CI: 1.08–57.37), lower mothers’ utilization of antenatal care (ANC) services (AOR:1.25; 95 % CI: 1.07–63.75), being the ≥3rd born child in the family (AOR: 425.4; 95 % CI: 9.6–18,808), younger mothers’ age (AOR: 49.55; 95 % CI: 1.59–1544), parents’ negative attitude towards immunization (AOR: 20.2; 95 % CI: 1.46–278.9), and poorer parents’ exposure to information on vaccination (AOR: 28.07; 95 % CI: 2.26–348.1). Longer distance from the vaccination centers was marginally significant (p = 0.05).
Vaccination coverage was high; however, 1 out of 7 children was partially vaccinated, and 1 out of 4 did not complete timely the recommended vaccinations. In order to improve the immunization coverage, it is necessary to strengthen ANC services, and to improve parents’ information and attitude towards immunization, targeting younger parents and families living far away from vaccination centers, using appropriate communication strategies. Finally, the estimated OPV-3 coverage is reassuring in relation to the ongoing polio outbreak.
PMCID: PMC4496879  PMID: 26156158
Vaccination coverage; Survey; Determinants of immunization; Children; Cameroon
4.  Validating child vaccination status in a demographic surveillance system using data from a clinical cohort study: evidence from rural South Africa 
BMC Public Health  2011;11:372.
Childhood vaccination coverage can be estimated from a range of sources. This study aims to validate vaccination data from a longitudinal population-based demographic surveillance system (DSS) against data from a clinical cohort study.
The sample includes 821 children in the Vertical Transmission cohort Study (VTS), who were born between December 2001 and April 2005, and were matched to the Africa Centre DSS, in northern KwaZulu-Natal. Vaccination information in the surveillance was collected retrospectively, using standardized questionnaires during bi-annual household visits, when the child was 12 to 23 months of age. DSS vaccination information was based on extraction from a vaccination card or, if the card was not available, on maternal recall. In the VTS, vaccination data was collected at scheduled maternal and child clinic visits when a study nurse administered child vaccinations. We estimated the sensitivity of the surveillance in detecting vaccinations conducted as part of the VTS during these clinic visits.
Vaccination data in matched children in the DSS was based on the vaccination card in about two-thirds of the cases and on maternal recall in about one-third. The sensitivity of the vaccination variables in the surveillance was high for all vaccines based on either information from a South African Road-to-Health (RTH) card (0.94-0.97) or maternal recall (0.94-0.98). Addition of maternal recall to the RTH card information had little effect on the sensitivity of the surveillance variable (0.95-0.97). The estimates of sensitivity did not vary significantly, when we stratified the analyses by maternal antenatal HIV status. Addition of maternal recall of vaccination status of the child to the RTH card information significantly increased the proportion of children known to be vaccinated across all vaccines in the DSS.
Maternal recall performs well in identifying vaccinated children aged 12-23 months (both in HIV-infected and HIV-uninfected mothers), with sensitivity similar to information extracted from vaccination cards. Information based on both maternal recall and vaccination cards should be used if the aim is to use surveillance data to identify children who received a vaccination.
PMCID: PMC3118246  PMID: 21605408
5.  Parental Delay or Refusal of Vaccine Doses, Childhood Vaccination Coverage at 24 Months of Age, and the Health Belief Model 
Public Health Reports  2011;126(Suppl 2):135-146.
We evaluated the association between parents' beliefs about vaccines, their decision to delay or refuse vaccines for their children, and vaccination coverage of children at aged 24 months.
We used data from 11,206 parents of children aged 24–35 months at the time of the 2009 National Immunization Survey interview and determined their vaccination status at aged 24 months. Data included parents' reports of delay and/or refusal of vaccine doses, psychosocial factors suggested by the Health Belief Model, and provider-reported up-to-date vaccination status.
In 2009, approximately 60.2% of parents with children aged 24–35 months neither delayed nor refused vaccines, 25.8% only delayed, 8.2% only refused, and 5.8% both delayed and refused vaccines. Compared with parents who neither delayed nor refused vaccines, parents who delayed and refused vaccines were significantly less likely to believe that vaccines are necessary to protect the health of children (70.1% vs. 96.2%), that their child might get a disease if they aren't vaccinated (71.0% vs. 90.0%), and that vaccines are safe (50.4% vs. 84.9%). Children of parents who delayed and refused also had significantly lower vaccination coverage for nine of the 10 recommended childhood vaccines including diphtheria-tetanus-acellular pertussis (65.3% vs. 85.2%), polio (76.9% vs. 93.8%), and measles-mumps-rubella (68.4% vs. 92.5%). After adjusting for sociodemographic differences, we found that parents who were less likely to agree that vaccines are necessary to protect the health of children, to believe that their child might get a disease if they aren't vaccinated, or to believe that vaccines are safe had significantly lower coverage for all 10 childhood vaccines.
Parents who delayed and refused vaccine doses were more likely to have vaccine safety concerns and perceive fewer benefits associated with vaccines. Guidelines published by the American Academy of Pediatrics may assist providers in responding to parents who may delay or refuse vaccines.
PMCID: PMC3113438  PMID: 21812176
6.  Measuring the Performance of Vaccination Programs Using Cross-Sectional Surveys: A Likelihood Framework and Retrospective Analysis 
PLoS Medicine  2011;8(10):e1001110.
Justin Lessler and colleagues describe a method that estimates the fraction of a population accessible to vaccination activities, and they apply it to measles vaccination in three African countries: Ghana, Madagascar, and Sierra Leone.
The performance of routine and supplemental immunization activities is usually measured by the administrative method: dividing the number of doses distributed by the size of the target population. This method leads to coverage estimates that are sometimes impossible (e.g., vaccination of 102% of the target population), and are generally inconsistent with the proportion found to be vaccinated in Demographic and Health Surveys (DHS). We describe a method that estimates the fraction of the population accessible to vaccination activities, as well as within-campaign inefficiencies, thus providing a consistent estimate of vaccination coverage.
Methods and Findings
We developed a likelihood framework for estimating the effective coverage of vaccination programs using cross-sectional surveys of vaccine coverage combined with administrative data. We applied our method to measles vaccination in three African countries: Ghana, Madagascar, and Sierra Leone, using data from each country's most recent DHS survey and administrative coverage data reported to the World Health Organization. We estimate that 93% (95% CI: 91, 94) of the population in Ghana was ever covered by any measles vaccination activity, 77% (95% CI: 78, 81) in Madagascar, and 69% (95% CI: 67, 70) in Sierra Leone. “Within-activity” inefficiencies were estimated to be low in Ghana, and higher in Sierra Leone and Madagascar. Our model successfully fits age-specific vaccination coverage levels seen in DHS data, which differ markedly from those predicted by naïve extrapolation from country-reported and World Health Organization–adjusted vaccination coverage.
Combining administrative data with survey data substantially improves estimates of vaccination coverage. Estimates of the inefficiency of past vaccination activities and the proportion not covered by any activity allow us to more accurately predict the results of future activities and provide insight into the ways in which vaccination programs are failing to meet their goals.
Please see later in the article for the Editors' Summary
Editors' Summary
Immunization (vaccination) is a proven, cost-effective tool for controlling life-threatening infectious diseases. It provides protection against infectious diseases by priming the human immune system to respond quickly and efficiently to bacteria, viruses, and other disease-causing organisms (pathogens). Whenever the human body is exposed to a pathogen, the immune system—a network of cells, tissues, and organs—mounts an attack against the foreign invader. Importantly, the immune system “learns” from the encounter, and the next time the body is exposed to the same pathogen, the immune system responds much faster to the threat. Immunization exposes the body to a very small amount of a pathogen, thereby safely providing protection against subsequent infection. More than two billion deaths are averted every year through routine childhood immunization and supplemental immunization activities (mass vaccination campaigns designed to increase vaccination coverage where immunization goals have not been reached by routine vaccination). Indeed, these two types of vaccination activities have eliminated smallpox from the world and are close to doing the same for several other infectious diseases.
Why Was This Study Done?
To reduce deaths from infectious diseases even further, it is important to know the proportion of the population reached by vaccination activities. At present, countries report vaccination coverage to the World Health Organization (WHO) that is calculated by dividing the number of vaccine doses delivered during the activity by the size of the target population. However, estimates arrived at through this “administrative method” do not account for vaccine doses that were not actually delivered, and can only reflect a single vaccination activity, which prevents us from identifying populations that may be systematically missed by all vaccination activities (for example, children living in remote areas, or children whose parents refuse vaccination). Moreover, estimates of coverage obtained by the administrative method rarely agree with estimates obtained through cross-sectional surveys such as Demographic and Health Surveys (DHS), which are household surveys of family circumstances and health undertaken at a single time point. In this study, the researchers developed a method for measuring the performance of vaccination activities that estimates the fraction of the population accessible to these activities and within-activity inefficiencies. They then tested their method by applying it to measles vaccination in three African countries; before 1980, measles killed about 2.6 million children worldwide every year, but vaccination activities have reduced this death toll to about 164,000 per year.
What Did the Researchers Do and Find?
The researchers developed a set of formulae (a “likelihood framework”) to estimate the effective coverage of vaccination activities using data on vaccine coverage from cross-sectional surveys and administrative data. They then applied their method to measles vaccination in Ghana, Madagascar, and Sierra Leone using data obtained in each country's most recent DHS survey and administrative data reported to WHO. The researchers estimate that 93%, 77%, and 65% of the target populations in Ghana, Madagascar, and Sierra Leone, respectively, were ever covered by any vaccination activity, and that inefficiencies within vaccination activities were low for Ghana, but higher for Madagascar and Sierra Leone. Consequently, the researchers' estimates of vaccination activity coverage were substantially lower than the administrative estimates for Madagascar and Sierra Leone but only slightly lower than that for Ghana. Finally, the researchers' estimates of routine vaccination coverage were generally lower than WHO-adjusted estimates but broadly agreed with age-specific vaccination coverage levels from DHS surveys.
What Do These Findings Mean?
Although the accuracy of the estimates provided by this likelihood framework depends on the assumptions included in the framework and the quality of the data fed into it, these findings show that, by combining administrative data with survey data, estimates of vaccine coverage can be substantially improved. By providing estimates of both the inefficiency of past vaccination activities and the proportion of the target population inaccessible to any vaccination activity, this method should help public health experts predict the results of future activities and help them understand why some vaccination programs fail to meet their goals. Importantly, knowing both the size of the inaccessible population and the inefficiency level of past programs makes it possible to estimate the effect of providing additional doses of vaccine on vaccination coverage. Finally, the application of this new method might help individual countries understand how susceptibility to specific infectious diseases is building up in their population and enable them to avoid outbreaks similar to the measles outbreaks that have recently occurred in several African countries.
Additional Information
Please access these Web sites via the online version of this summary at
WHO provides information about immunization and details of its Expanded Program on Immunization and its Global Immunization Vision and Strategy; WHO Africa provides details about measles immunization in Africa; a photo story about mass measles vaccination in Côte d’Ivoire is available (some material in several languages)
The UK National Health Service Choices website provides information for members of the public about immunization
The Measles Initiative is a collaborative effort that aims to reduce global measles mortality through mass vaccination campaigns and by strengthening routine immunization; its website includes information on measles and measles vaccination, including photos and videos of vaccination activities
MedlinePlus provides links to additional resources about immunization and about measles (in English and Spanish)
The charity website Healthtalkonline has interviews with UK parents about their experience of immunizing their children
PMCID: PMC3201935  PMID: 22039353
7.  Factors associated with underimmunization at 3 months of age in four medically underserved areas. 
Public Health Reports  2004;119(5):479-485.
OBJECTIVE: Risk factors for underimmunization at 3 months of age are not well described. This study examines coverage rates and factors associated with under-immunization at 3 months of age in four medically underserved areas. METHODS: During 1997-1998, cross-sectional household surveys using a two-stage cluster sample design were conducted in four federally designated Health Professional Shortage Areas. Respondents were parents or caregivers of children ages 12-35 months: 847 from northern Manhattan, 843 from Detroit, 771 from San Diego, and 1,091 from rural Colorado. A child was considered up-to-date (UTD) with vaccinations at 3 months of age if documentation of receipt of diphtheria-tetanus-pertussis, polio, haemophilus influenzae type B, and hepatitis B vaccines was obtained from a provider or a hand-held vaccination card, or both. RESULTS: Household response rates ranged from 79% to 88% across sites. Vaccination coverage levels at 3 months of age varied across sites: 82.4% in northern Manhattan, 70.5% in Detroit, 82.3% in San Diego, and 75.8% in rural Colorado. Among children who were not UTD, the majority (65.7% to 71.5% per site) had missed vaccines due to missed opportunities. Factors associated with not being UTD varied by site and included having public or no insurance, >/=2 children living in the household, and the adult respondent being unmarried. At all sites, vaccination coverage among WIC enrollees was higher than coverage among children eligible for but not enrolled in WIC, but the association between UTD status and WIC enrollment was statistically significant for only one site and marginally significant for two other sites. CONCLUSIONS: Missed opportunities were a significant barrier to vaccinations, even at this early age. Practice-based strategies to reduce missed opportunities and prenatal WIC enrollment should be focused especially toward those at highest risk of underimmunization.
PMCID: PMC1497657  PMID: 15313111
8.  The Association Between Intentional Delay of Vaccine Administration and Timely Childhood Vaccination Coverage 
Public Health Reports  2010;125(4):534-541.
We evaluated the association between intentional delay of vaccine administration and timely vaccination coverage.
We used data from 2,921 parents of 19- to 35-month-old children that included parents' reports of intentional delay of vaccine administration. Timely vaccination was defined as administration with ≥4 doses of diphtheria, tetanus, and pertussis; ≥3 doses of polio vaccine; ≥1 dose of measles, mumps, and rubella vaccine; ≥3 doses of Haemophilus influenzae type b vaccine; ≥3 doses of hepatitis B vaccine; and ≥1 dose of varicella vaccine by 19 months of age, as reported by vaccination providers.
In all, 21.8% of parents reported intentionally delaying vaccinations for their children. Among parents who intentionally delayed, 44.8% did so because of concerns about vaccine safety or efficacy and 36.1% delayed because of an ill child. Children whose parents intentionally delayed were significantly less likely to receive all vaccines by 19 months of age than children whose parents did not delay (35.4% vs. 60.1%, p<0.05). Parents who intentionally delayed were significantly more likely to have heard or read unfavorable information about vaccines than parents who did not intentionally delay (87.6% vs. 71.9%, p<0.05). Compared with parents who intentionally delayed only because their child was ill, parents who intentionally delayed only because of vaccine safety or efficacy concerns were significantly more likely to seek additional information about their decision from the Internet (11.4% vs. 1.1%, p<0.05), and significantly less likely to seek information from a doctor (73.9% vs. 93.9%, p<0.05).
Intentionally delayed vaccine doses are not uncommon. Children whose parents delay vaccinations may be at increased risk of not receiving all recommended vaccine doses by 19 months of age and are more vulnerable to vaccine-preventable diseases. Providers should consider strategies such as educational materials that address parents' vaccine safety and efficacy concerns to encourage timely vaccination.
PMCID: PMC2882604  PMID: 20597453
9.  The association between travel time to health facilities and childhood vaccine coverage in rural Ethiopia. A community based cross sectional study 
BMC Public Health  2012;12:476.
Few studies have examined associations between access to health care and childhood vaccine coverage in remote communities that lack motorised transport. This study assessed whether travel time to health facilities was associated with childhood vaccine coverage in a remote area of Ethiopia.
This was a cross-sectional study using data from 775 children aged 12–59 months who participated in a household survey between January –July 2010 in Dabat district, north-western Ethiopia. 208 households were randomly selected from each kebele. All children in a household were eligible for inclusion if they were aged between 12–59 months at the time of data collection. Travel time to vaccine providers was collected using a geographical information system (GIS). The primary outcome was the percentage of children in the study population who were vaccinated with the third infant Pentavalent vaccine ([Diphtheria, Tetanus,-Pertussis Hepatitis B, Haemophilus influenza type b] Penta3) in the five years before the survey. We also assessed effects on BCG, Penta1, Penta2 and Measles vaccines. Analysis was conducted using Poisson regression models with robust standard error estimation and the Wald test.
Missing vaccination data ranged from 4.6% (36/775) for BCG to 16.4% (127/775) for Penta3 vaccine. In children with complete vaccination records, BCG vaccine had the highest coverage (97.3% [719/739]), Penta3 coverage was (92.9% [602/648]) and Measles vaccine had the lowest coverage (81.7% [564/690]). Children living ≥60mins from a health post were significantly less likely (adjRR = 0.85 [0.79-0.92] p value < =0.001) to receive Penta3 vaccine compared to children living <30mins from a health post. This effect was not modified by household wealth (p value = 0.240). Travel time also had a highly significant association with BCG (adjRR = 0.95 [0.93-0.98] p value =0.002) and Measles (adjRR = 0.88 [0.79-0.97] p value =0.027) vaccine coverage.
Travel time to vaccine providers in health posts appeared to be a barrier to the delivery of infant vaccines in this remote Ethiopian community. New vaccine delivery strategies are needed for the hardest to reach children in the African region.
PMCID: PMC3439329  PMID: 22726457
10.  Does the effect of vitamin A supplements depend on vaccination status? An observational study from Guinea-Bissau 
BMJ Open  2012;2(1):e000448.
Vitamin A supplementation (VAS) is estimated to reduce all-cause mortality by 24%. Previous studies indicate that the effect of VAS may vary with vaccination status. The authors evaluated the effect of VAS provided in campaigns on child survival overall and by sex and vaccination status at the time of supplementation.
Observational cohort study.
Setting and participants
The study was conducted in the urban study area of the Bandim Health Project in Guinea-Bissau. The authors documented participation or non-participation in two national vitamin A campaigns in December 2007 and July 2008 for children between 6 and 35 months of age. Vaccination status was ascertained by inspection of vaccination cards. All children were followed prospectively.
Outcome measures
Mortality rates for supplemented and non-supplemented children were compared in Cox models providing mortality rate ratios (MRRs).
The authors obtained information from 93% of 5567 children in 2007 and 90% of 5799 children in 2008. The VAS coverage was 58% in 2007 and 68% in 2008. Mortality in the supplemented group was 1.5% (44 deaths/2873 person-years) and 1.6% (20 deaths/1260 person-years) in the non-supplemented group (adjusted MRR=0.78 (0.46; 1.34)). The effect was similar in boys and girls. Vaccination cards were seen for 86% in 2007 and 84% in 2008. The effect of VAS in children who had measles vaccine as their last vaccine (2814 children, adjusted MRR=0.34 (0.14; 0.85)) differed from the effect in children who had diphtheria–tetanus–pertussis vaccine as their last vaccine (3680 children, adjusted MRR=1.29 (0.52; 3.22), p=0.04 for interaction).
The effect of VAS differed by most recent vaccination, being beneficial after measles vaccine but not after diphtheria–tetanus–pertussis vaccine.
Article summary
Article focus
Vitamin A supplementation (VAS) is estimated to reduce all-cause mortality by 24%.
The effect of VAS may vary with vaccination status, being beneficial with or after measles vaccine (MV) but not after diphtheria–tetanus–pertussis (DTP) vaccine.
Key messages
The effect of VAS is heterogeneous.
The effect of VAS varied with vaccination status: supplemented children had lower mortality than non-supplemented children when MV was the most recent vaccine but not when DTP was the most recent vaccine.
The effect of VAS tended to differ by season of supplementation.
Strengths and limitations of this study
Information was collected on the individual level, and the children were followed prospectively.
Due to the observational nature of the study, the comparison of supplemented and non-supplemented children should be interpreted with caution.
However, a selection bias is unlikely to have worked in different directions for children who had DTP and MV as the most recent vaccine.
PMCID: PMC3278485  PMID: 22240648
11.  How do caregivers know when to take their child for immunizations? 
BMC Pediatrics  2005;5:44.
Childhood vaccinations help reduce and eliminate many causes of morbidity and mortality among children. The objective of this study was to compare 4:3:1:3:3 (4+ doses of diphtheria and tetanus toxoids and pertussis vaccine, 3+ doses of poliovirus vaccine, 1+ doses of measles-containing vaccine, 3+ doses of Haemophilus influenzae type b vaccine, and 3+ doses of hepatitis B vaccine) coverage among children whose caregivers learned by different methods when their child's most recent immunization was needed.
Between July 2001 and December 2002, a portion of households receiving the National Immunization Survey were asked how they knew when to take the child in for his/her most recent immunization. Responses were post-coded into several categories: 'Doctor/nurse reminder at previous immunization visit', 'Shot card/record', 'Reminder/recall', and 'Other'. Respondents could give more than one answer. Children who did not receive any vaccines, had ≤ 1 visits for vaccinations, or whose caregiver did not provide an answer to the question were excluded from analyses. Chi-square analyses were used to compare 4:3:1:3:3 coverage among 19–35 month old children.
Children whose caregivers indicated that a doctor/nurse told them at a previous immunization visit when to return for the next immunization had significantly greater 4:3:1:3:3 coverage than those who did not choose the response (77.2% vs. 70.1%, p < 0.01). However, no significant difference in coverage was found between households that did/did not indicate that reminder/recalls (71.0% vs. 75.5%, p = 0.24) helped them remember when to take their child for their most recent immunization visit; only borderline significance was found between those that did/did not choose shot cards (70.6% vs. 76.2%, p = 0.07).
A doctor or nurse's reminder during an immunization visit of the next scheduled immunization visit effectively encourages caregivers to bring children in for immunizations, providing an inexpensive and easy way to effectively increase immunization coverage.
PMCID: PMC1314897  PMID: 16316458
12.  Evaluation of immunization coverage within the Expanded Program on Immunization in Kita Circle, Mali: a cross-sectional survey 
In 1986, the Government of Mali launched its Expanded Program on Immunization (EPI) with the goal of vaccinating, within five years, 80% of all children under the age of five against six target diseases: diphtheria, tetanus, pertussis, poliomyelitis, tuberculosis, and measles. The Demographic and Health Survey carried out in 2001 revealed that, in Kita Circle, in the Kayes region, only 13% of children aged 12 to 23 months had received all the EPI vaccinations. A priority program was implemented in 2003 by the Regional Health Department in Kayes to improve EPI immunization coverage in this area.
A cross-sectional survey using Henderson's method (following the method used by the Demographic and Health Surveys) was carried out in July 2006 to determine the level of vaccination coverage among children aged 12 to 23 months in Kita Circle, after implementation of the priority program. Both vaccination cards and mothers' declarations (in cases where the mother cannot make the declaration, it is made by the person responsible for the child) were used to determine coverage.
According to the vaccination cards, 59.9% [CI 95% (54.7-64.8)] of the children were fully vaccinated, while according to the mothers' declarations the rate was 74.1% [CI 95% (69.3-78.4)]. The drop-out rate between DTCP1 and DTCP3 was 5.5%, according to the vaccination cards. The rate of immunization coverage was higher among children whose mothers had received the anti-tetanus vaccine [OR = 2.1, CI 95% (1.44-3.28)]. However, our study found no difference associated with parents' knowledge about EPI diseases, distance from the health centre, or socio-economic status. Lack of information was one reason given for children not being vaccinated against the six EPI diseases.
Three years after the implementation of the priority program (which included decentralization, the active search for missing children, and deployment of health personnel, material and financial resources), our evaluation of the vaccination coverage rates shows that there is improvement in the EPI immunization coverage rate in Kita Circle. The design of our study did not, however, enable us to determine the extent to which different aspects of the program contributed to this increase in coverage. Efforts should nevertheless be continued, in order to reach the goal of 80% immunization coverage.
Abstract in French
See the full article online for a translation of this abstract in French.
PMCID: PMC3226232  PMID: 19828057
13.  Vaccination Coverage Estimates for Selected Counties: Achievement of Healthy People 2010 Goals and Association with Indices of Access to Care, Economic Conditions, and Demographic Composition 
Public Health Reports  2008;123(2):155-172.
We provided vaccination coverage estimates for 181 counties; evaluated the extent to which Healthy People 2010 (HP 2010) vaccination coverage objectives were achieved; and examined how variations in those estimates depend on access to care and economic conditions.
We analyzed data for 24,031 children aged 19 to 35 months sampled from the 2004 and 2005 National Immunization Survey.
Children living in the 181 counties represented 49% of all the 19- to 35-month-old children living in the U.S. None of the 181 counties had coverage for the polio, measles-mumps-rubella, Haemophilus influenzae type B, and hepatitis B vaccines that was significantly lower than the HP 2010 objective of 90% coverage. However, as many as 30.4% of the counties did not achieve the HP 2010 objective for diphtheria, tetanus toxoids, and acellular pertussis or diphtheria and tetanus toxoids and pertussis (DtaP/DTP), and as many as 6.6% did not achieve the goal for varicella (VAR). If children who received three doses of DTaP/DTP had received a final fourth dose, and if all children had received one dose of VAR, all of the 181 counties would have achieved the HP 2010 vaccination coverage target of 80% for the entire 4:3:1:3:3:1 vaccination series. Factors found to be associated with low county-level vaccination coverage rates were correlates of poverty, and factors found to be associated with high county-level vaccination coverage rates were correlates of access to pediatric services.
HP 2010 vaccination coverage goals for all 181 counties can be achieved by improving vaccination coverage for only two vaccines. Those goals may be achieved most efficiently by targeting interventions in counties where indices of poverty are high or where access to pediatric services is low.
PMCID: PMC2239325  PMID: 18457068
14.  The Swiss National Vaccination Coverage Survey, 2005–2007 
Public Health Reports  2011;126(Suppl 2):97-108.
We described the results from the Swiss National Vaccination Coverage Survey (SNVCS) 2005–2007, a survey designed to monitor immunization coverage of children and adolescents residing in Switzerland in each canton within a three-year period.
The SNVCS is a cross-sectional survey using a two-stage sampling design targeting children aged 2, 8, and 16 years. Families of selected children were contacted by mail and telephone. Coverage was determined via vaccination cards or vaccination summary forms.
A total of 25 out of 26 cantons participated in the survey, with 8,286 respondents for children aged 24–35 months, 10,314 respondents for children aged 8 years, and 9,301 respondents for teenagers aged 16 years. Compared with data from 1999–2003, coverage estimates for toddlers remained unchanged for diphtheria, tetanus, pertussis, poliomyelitis, and Haemophilus influenzae type b vaccines at three doses, but increased five percentage points to 86%–87% for measles-mumps-rubella at one dose and was 71% at two doses. Coverage for measles, mumps, and rubella were 89%–90% at one dose and 75% at two doses for 8-year-olds, and 94% and 76% for the two dosages, respectively, for 16-year-olds. Linguistic region and nationality were highly correlated with being vaccinated against measles for the two younger age groups.
Despite the increase in vaccine coverage, measles vaccination is still low, and the World Health Organization goal to eliminate measles by 2010 was not achieved in Switzerland. More efforts are needed by the cantons and the central government to increase vaccination coverage.
PMCID: PMC3113435  PMID: 21812174
15.  Compulsory and recommended vaccination in Italy: evaluation of coverage and non-compliance between 1998-2002 in Northern Italy 
BMC Public Health  2005;5:42.
Since vaccinations are an effective prevention tool for maintaining the health of society, the monitoring of immunization coverage allows us to identify areas where disease outbreaks are likely to occur, and possibly assist us in predicting future outbreaks. The aim of this study is the investigation of the coverage achieved for compulsory (diphtheria, tetanus, polio, hepatitis B,) and recommended (pertussis, Haemophilus influenzae, measles-mumps-rubella) vaccinations between 1998 and 2002 in the municipality of Bologna and the identification of the subjects not complying with compulsory and recommended vaccinations.
The statistics regarding vaccinal coverage were elaborated from the data supplied by the Bologna vaccinal registration system (1998–2000) and the IPV4 program (2001–2002). To calculate the coverage for compulsory vaccinations and cases of non-compliance reference was made to the protocol drawn up by the Emilia Romagna Regional Administration. The reasons for non-compliance were divided into various categories
In Bologna the levels of immunization for the four compulsory vaccinations are satisfactory: over 95% children completed the vaccinal cycle, receiving the booster for anti-polio foreseen in their 3rd year and for anti-dyphteria, tetanus, pertussis at 6 years. The frequency of subjects with total non-compliance (i.e. those who have not begun any compulsory vaccinations by the age of one year) is generally higher in Bologna than in the region, with a slight increase in 2002 (2.52% and 1.06% in the city and the region respectively). The frequency of the anti-measles vaccination is higher than that of mumps and rubella, which means that the single vaccine, as opposed to the combined MMR (measles-mumps-rubella) was still being used in the period in question.
The most common reason for non compliance is objection of parents and is probably due to reduction of certain diseases or anxiety about the possible risks.
In Bologna the frequency of children aged 12 and 24 months who have achieved compulsory vaccination varied, in 2002, between 95% and 98%. As regards recommended vaccinations the percentage of coverage against Haemophilus influenzae is 93.3%, while the levels for measles, mumps and pertussis range from 84% to approx. 92%. Although these percentages are higher if compared to those obtained by other Italian regions, every effort should be made to strengthen the aspects that lead to a successful vaccinal strategy.
PMCID: PMC1090596  PMID: 15845144
16.  An evaluation of the 2012 measles mass vaccination campaign in Guinea 
To estimate the post-campaign level of measles vaccination coverage in Guinea.
Interview of parents and observation of measles vaccination cards of children aged 9 to 59 months during the mass measles campaign. A nationwide cluster randomized sample under health District stratification.
64.2% (95%CI = 60.9% to 67.4%) of children were vaccinated and had their measles vaccination card. With respect to card and history 90.5% (95%CI = 88.3% to 92.3%) were vaccinated. The estimation was found to be between 72.7% and 81.9%. Coverage with card increased from 55.5% to 79.30% with the level of education of parents but that was not statistically significant, (X2(trend) =3.087 P= 0.07). However coverage with card significantly increased with profession from 55.1% for farmers followed by 59.2% for other manual workers to 73.8% for sellers, ending by 74.5% for settled technicians (X2 (trend) =12.16 P= 0.0005). For unvaccinated children, lack of information accounted for the main reason (37.03%) followed by parents’ occupation (23.45%), parents’ sickness (8.6%), children's sickness (4.9%) and others including vaccinators absent in the post or parents’ belief that it was a door to door campaign.
The mass measles vaccination campaign achieved an approximate coverage of 75%. Although not enough for effective control of measles, it has covered an important gap left over by the routine immunization coverage 42%. Appropriate measures are needed to improve coverage in routine immunization and specific actions should be taken to target farmers and other manual workers’ families but also uneducated groups for both routine immunization and mass campaigns.
PMCID: PMC4149790  PMID: 25184021
Measles; immunization; evaluation; vaccination; coverage
17.  Determinants of vaccination coverage in rural Nigeria 
BMC Public Health  2008;8:381.
Childhood immunization is a cost effective public health strategy. Expanded Programme on Immunisation (EPI) services have been provided in a rural Nigerian community (Sabongidda-Ora, Edo State) at no cost to the community since 1998 through a privately financed vaccination project (private public partnership). The objective of this survey was to assess vaccination coverage and its determinants in this rural community in Nigeria
A cross-sectional survey was conducted in September 2006, which included the use of interviewer-administered questionnaire to assess knowledge of mothers of children aged 12–23 months and vaccination coverage. Survey participants were selected following the World Health Organization's (WHO) immunization coverage cluster survey design. Vaccination coverage was assessed by vaccination card and maternal history. A child was said to be fully immunized if he or she had received all of the following vaccines: a dose of Bacille Calmette Guerin (BCG), three doses of oral polio (OPV), three doses of diphtheria, pertussis and tetanus (DPT), three doses of hepatitis B (HB) and one dose of measles by the time he or she was enrolled in the survey, i.e. between the ages of 12–23 months. Knowledge of the mothers was graded as satisfactory if mothers had at least a score of 3 out of a maximum of 5 points. Logistic regression was performed to identify determinants of full immunization status.
Three hundred and thirty-nine mothers and 339 children (each mother had one eligible child) were included in the survey. Most of the mothers (99.1%) had very positive attitudes to immunization and > 55% were generally knowledgeable about symptoms of vaccine preventable diseases except for difficulty in breathing (as symptom of diphtheria). Two hundred and ninety-five mothers (87.0%) had a satisfactory level of knowledge. Vaccination coverage against all the seven childhood vaccine preventable diseases was 61.9% although it was significantly higher (p = 0.002) amongst those who had a vaccination card (131/188, 69.7%) than in those assessed by maternal history (79/151, 52.3%). Multiple logistic regression showed that mothers' knowledge of immunization (p = 0.006) and vaccination at a privately funded health facility (p < 0.001) were significantly correlated with the rate of full immunization.
Eight years after initiation of this privately financed vaccination project (private-public partnership), vaccination coverage in this rural community is at a level that provides high protection (81%) against DPT/OPV. Completeness of vaccination was significantly correlated with knowledge of mothers on immunization and adequate attention should be given to this if high coverage levels are to be sustained.
PMCID: PMC2587468  PMID: 18986544
18.  Seasonal Influenza Vaccination for Children in Thailand: A Cost-Effectiveness Analysis 
PLoS Medicine  2015;12(5):e1001829.
Seasonal influenza is a major cause of mortality worldwide. Routine immunization of children has the potential to reduce this mortality through both direct and indirect protection, but has not been adopted by any low- or middle-income countries. We developed a framework to evaluate the cost-effectiveness of influenza vaccination policies in developing countries and used it to consider annual vaccination of school- and preschool-aged children with either trivalent inactivated influenza vaccine (TIV) or trivalent live-attenuated influenza vaccine (LAIV) in Thailand. We also compared these approaches with a policy of expanding TIV coverage in the elderly.
Methods and Findings
We developed an age-structured model to evaluate the cost-effectiveness of eight vaccination policies parameterized using country-level data from Thailand. For policies using LAIV, we considered five different age groups of children to vaccinate. We adopted a Bayesian evidence-synthesis framework, expressing uncertainty in parameters through probability distributions derived by fitting the model to prospectively collected laboratory-confirmed influenza data from 2005-2009, by meta-analysis of clinical trial data, and by using prior probability distributions derived from literature review and elicitation of expert opinion. We performed sensitivity analyses using alternative assumptions about prior immunity, contact patterns between age groups, the proportion of infections that are symptomatic, cost per unit vaccine, and vaccine effectiveness. Vaccination of children with LAIV was found to be highly cost-effective, with incremental cost-effectiveness ratios between about 2,000 and 5,000 international dollars per disability-adjusted life year averted, and was consistently preferred to TIV-based policies. These findings were robust to extensive sensitivity analyses. The optimal age group to vaccinate with LAIV, however, was sensitive both to the willingness to pay for health benefits and to assumptions about contact patterns between age groups.
Vaccinating school-aged children with LAIV is likely to be cost-effective in Thailand in the short term, though the long-term consequences of such a policy cannot be reliably predicted given current knowledge of influenza epidemiology and immunology. Our work provides a coherent framework that can be used for similar analyses in other low- and middle-income countries.
Ben Cooper and colleagues use an age-structured model to estimate optimal cost-effectiveness of flu vaccination among Thai children aged 2 to 17.
Editors' Summary
Every year, millions of people catch influenza, a viral disease of the airways. Most infected individuals recover quickly, but elderly people, the very young, and chronically ill individuals are at high risk of developing serious complications such as pneumonia; seasonal influenza kills about half a million people annually. Small but frequent changes in the influenza virus mean that an immune response produced one year by exposure to the virus provides only partial protection against influenza the next year. Annual immunization with a vaccine that contains killed or live-attenuated (weakened) influenza viruses of the major circulating strains can reduce a person’s chance of catching influenza. Consequently, many countries run seasonal influenza vaccination programs that target elderly people and other people at high risk of influenza complications, and people who care for these individuals.
Why Was This Study Done?
As well as reducing the vaccinated person’s risk of infection, influenza vaccination protects unvaccinated members of the population by reducing the chances of influenza spreading. Because children make a disproportionately large contribution to the transmission of influenza, vaccination of children might therefore provide greater benefits to the whole population than vaccination of elderly people, particularly when vaccination uptake among the elderly is low. Thus, many high-income countries now recommend annual influenza vaccination of children with a trivalent live-attenuated influenza vaccine (LAIV; a trivalent vaccine contains three viruses), which is sprayed into the nose. However, to date no low- or middle-income countries have evaluated this policy. Here, the researchers develop a mathematical model (framework) to evaluate the cost-effectiveness of annual vaccination of children with LAIV or trivalent inactivated influenza vaccine (TIV) in Thailand. A cost-effectiveness analysis evaluates whether a medical intervention is good value for money by comparing the health outcomes and costs associated with the introduction of the intervention with the health outcomes and costs of the existing standard of care. Thailand, a middle-income country, offers everyone over 65 years old free seasonal influenza vaccination with TIV, but vaccine coverage in this age group is low (10%).
What Did the Researchers Do and Find?
The researchers developed a modeling framework that contained six connected components including a transmission model that incorporated infectious contacts within and between different age groups, a health outcome model that calculated the disability-adjusted life years (DALYs, a measure of the overall disease burden) averted by specific vaccination policies, and a cost model that calculated the costs to the population of each policy. They used this framework and data from Thailand to calculate the cost-effectiveness of six childhood vaccination policies in Thailand (one with TIV and five with LAIV that targeted children of different ages) against a baseline policy of 10% TIV coverage in the elderly; they also investigated the cost-effectiveness of increasing vaccination in the elderly to 66%. All seven vaccination policies tested reduced influenza cases and deaths compared to the baseline policy, but the LAIV-based polices were consistently better than the TIV-based policies; the smallest reductions were seen when TIV coverage in elderly people was increased to 66%. All seven policies were highly cost-effective according to the World Health Organization’s threshold for cost-effectiveness. That is, the cost per DALY averted by each policy compared to the baseline policy (the incremental cost-effectiveness ratio) was less than Thailand’s gross domestic product per capita (the total economic output of a country divided by the number of people in the country).
What Do These Findings Mean?
These findings suggest that seasonal influenza vaccination of children with LAIV is likely to represent good value for money in Thailand and, potentially, in other middle- and low-income countries in the short term. The long-term consequences of annual influenza vaccination of children in Thailand cannot be reliably predicted, however, because of limitations in our current understanding of influenza immunity in populations. Moreover, the accuracy of these findings is limited by the assumptions built into the modeling framework, including the vaccine costs and efficacy that were used to run the model, which were estimated from limited data. Importantly, however, these findings support proposals for large-scale community-based controlled trials of policies to vaccinate children against influenza in low- and middle-income countries. Indeed, based on these findings, Thailand is planning to evaluate school-based seasonal influenza vaccination in a few provinces in 2016 before considering a nationwide program of seasonal influenza vaccination of children.
Additional Information
This list of resources contains links that can be accessed when viewing the PDF on a device or via the online version of the article at
The UK National Health Service Choices website provides information for patients about seasonal influenza, about influenza vaccination, and about influenza vaccination in children
The World Health Organization provides information on seasonal influenza (in several languages) and on influenza vaccines
The US Centers for Disease Control and Prevention also provides information for patients and health professionals on all aspects of seasonal influenza, including information about vaccination, about children, influenza, and vaccination, and about herd immunity; its website contains a short video about personal experiences of influenza, a US government website, provides access to information on seasonal influenza and vaccination
MedlinePlus has links to further information about influenza and about vaccination (in English and Spanish)
The Thai National Influenza Center monitors influenza activity throughout Thailand
PMCID: PMC4444096  PMID: 26011712
19.  Lot quality survey: an appealing method for rapid evaluation of vaccine coverage in developing countries – experience in Turkey 
BMC Public Health  2008;8:240.
Vaccine-preventable diseases cause significant morbidity and mortality worldwide and in developing countries in particular. Information on coverage and reasons for non-vaccination is vital to enhance overall vaccination activities. Of the several survey techniques available for investigating vaccination coverage in a given setting, the Lot Quality Technique (LQT) remains appealing and could be used in developing countries by local health personnel of district or rural health authorities to evaluate their performance in vaccination and many other health-related programs. This study aimed to evaluate vaccination coverage using LQT in a selected semi-urban setting in Turkey.
A LQT-based cross-sectional study was conducted in Kecioren District on a representative sample of residents aged 12–23 months in order to evaluate coverage for routine childhood vaccines, to identify health units with coverage below 75%, and to investigate reasons for non-vaccination.
Based on self-reports, coverage for BCG, diphtheria-pertussis-tetanus (DPT-3), oral polio-3, hepatitis-3, and measles vaccines ranged between 94–99%. Coverage for measles was below 75% in five lots. The relatively high educational and socioeconomic status of parents in the study group alone could not minimize the "considerable" risk of vaccine-preventable diseases in the District and dictates a continuity of efforts for improving vaccination rates, with special emphasis on measles. We believe that administrative methods should be backed up by household surveys to strengthen vaccination monitoring and that families should be trained and motivated to have their children fully vaccinated according to the recommended schedule and in a timely manner.
This study identified vaccine coverage for seven routine vaccines completed before the age of 24 months as well as the areas requiring special attention in vaccination services. The LQT, years after its introduction to health-related research, remains an appealing technique for rapid evaluation of the extent of a variety of local health concerns in developing countries, in rural areas in particular, and is very efficient in determining performance of individual subunits in a given service area. Training of local health personnel on use of the LQT could expedite response to local health problems and could even motivate them in conducting their own surveys tailored to their professional interests.
PMCID: PMC2483711  PMID: 18631382
20.  Effect of reminder notices on the timeliness of early childhood immunizations 
Paediatrics & Child Health  1999;4(6):400-405.
To determine whether reminder notices would improve the timeliness of toddler-age vaccinations.
Prospective, randomized, controlled trial.
Two convenience cohorts of 320 children due to receive either measles-mumps-rubella (MMR) vaccine (at 12 months of age) or diphtheria-pertussis-tetanus (DPT)-inactivated polio (IPV)- Haemophilus influenzae type b (Hib) booster vaccine (at 18 months of age).
Suburban community.
Parents of the identified children were randomly assigned either to a group to receive a reminder notice of pending vaccinations or a control group that did not receive a notice at a ratio of 1:1. Immunization uptake was assessed eights weeks after the initial due date for vaccination.
Information was obtained for 224 children in the MMR group and 227 children in the DPT-IPV-Hib booster group. MMR uptake within eight weeks of the due date was about 90% in both the test and control groups, probably because of publicity surrounding a local college-based measles outbreak. In the DPT-IPV-Hib group, reminder notices had no effect; the uptake rates within eight weeks of the due date were 73.7% to 75.2%. Delays in immunization resulted mostly from parents’ scheduling problems and provider-recommended delays. More than half of the parents whose child had delayed immunization did not recall receiving the reminder notice.
Mailed reminders did not increase on-time immunization rates in the second year of a child’s life. A telephone call or a more memorable reminder notice may be better suited to catch the attention of parents.
PMCID: PMC2827742  PMID: 20212950
Childhood; Immunization; Reminder notice
21.  HBV immunization and vaccine coverage among hospitalized children in Cameroon, Central African Republic and Senegal: a cross-sectional study 
BMC Infectious Diseases  2015;15:267.
Hepatitis B is a major health concern in Africa. The vaccine against hepatitis B virus (HBV) was introduced into the Expanded Programme on Immunization (EPI) of Cameroon and Senegal in 2005, and of CAR (Central African Republic) in 2008. A cross-sectional study was conducted to assess HBV immunization coverage following the vaccine’s introduction into the EPI and factors associated with having been vaccinated.
All hospitalized children, regardless of the reasons for their hospitalization, between 3 months and 6 years of age, for whom a blood test was scheduled during their stay and whose condition allowed for an additional 2 mL blood sample to be taken, and who provided the parent’s written consent were included. All children anti-HBs- and anti-HBc + were tested for HBsAg.
Vaccination coverage was assessed in three different ways: immunization card, maternal recall and serologic anti-HBs profile.
1783 children were enrolled between April 2009 and May 2010. An immunization card was only available for 24 % of the children. The median age was 21 months.
Overall HBV immunization coverage based on immunization cards was 99 %, 49 % and 100 % in Cameroon, CAR and Senegal, respectively (p < 0,001). The immunization rate based on maternal recall was 91 %, 17 % and 88 % in Cameroon, CAR and Senegal, respectively (p < 0,001). According to serology (anti-HBs titer ≥ 10 mUI/mL and anti-HBc-), the coverage rate was 68 %, 13 % and 46 % in Cameroon, CAR and Senegal, respectively (p < 0,001). In Senegal and Cameroon, factors associated with having been vaccinated were: mother’s higher education (OR = 2.2; 95 % CI [1.5–3.2]), no malnutrition (OR = 1.6; 95 % CI [1.1–2.2]), access to flushing toilets (OR = 1.6; 95 % CI [1.1–2.3]), and < 24 months old (OR = 2.1; 95 % CI [1.3–3.4] between 12 and 23 months and OR = 2.7; 95 % CI [1.6–4.4] < 12 months). The prevalence of HBV-infected children (HBsAg+) were 0.7 %, 5.1 %, and 0.2 % in Cameroon, CAR and Senegal, respectively (p < 0.001).
Assessing immunization coverage based on immunization cards, maternal recall or administrative data could be usefully reinforced by epidemiological data combined with immunological profiles. Serology-based studies should be implemented regularly in African countries, as recommended by the WHO. Malnutrition, lack of maternal education and poverty are factors associated with vaccine non-compliance. The countries’ vaccination programs should actively address these problems.
Electronic supplementary material
The online version of this article (doi:10.1186/s12879-015-1000-2) contains supplementary material, which is available to authorized users.
PMCID: PMC4499446  PMID: 26164361
HBV markers; HBV vaccine; African children; Cross-sectional survey
22.  Childhood vaccination in informal urban settlements in Nairobi, Kenya: Who gets vaccinated? 
BMC Public Health  2011;11:6.
Recent trends in global vaccination coverage have shown increases with most countries reaching 90% DTP3 coverage in 2008, although pockets of undervaccination continue to persist in parts of sub-Saharan Africa particularly in the urban slums. The objectives of this study were to determine the vaccination status of children aged between 12-23 months living in two slums of Nairobi and to identify the risk factors associated with incomplete vaccination.
The study was carried out as part of a longitudinal Maternal and Child Health study undertaken in Korogocho and Viwandani slums of Nairobi. These slums host the Nairobi Urban Health and Demographic Surveillance System (NUHDSS) run by the African Population and Health Research Centre (APHRC). All women from the NUHDSS area who gave birth since September 2006 were enrolled in the project and administered a questionnaire which asked about the vaccination history of their children. For the purpose of this study, we used data from 1848 children aged 12-23 months who were expected to have received all the WHO-recommended vaccinations. The vaccination details were collected during the first visit about four months after birth with follow-up visits repeated thereafter at four month intervals. Full vaccination was defined as receiving all the basic childhood vaccinations by the end of 24 months of life, whereas up-to-date (UTD) vaccination referred to receipt of BCG, OPV 1-3, DTP 1-3, and measles vaccinations within the first 12 months of life. All vaccination data were obtained from vaccination cards which were sighted during the household visit as well as by recall from mothers. Multivariate models were used to identify the risk factors associated with incomplete vaccination.
Measles coverage was substantially lower than that for the other vaccines when determined using only vaccination cards or in addition to maternal recall. Up-to-date (UTD) coverage with all vaccinations at 12 months was 41.3% and 51.8% with and without the birth dose of OPV, respectively. Full vaccination coverage (57.5%) was higher than up-to-date coverage (51.8%) at 12 months overall, and in both slum settlements, using data from cards. Multivariate analysis showed that household assets and expenditure, ethnicity, place of delivery, mother's level of education, age and parity were all predictors of full vaccination among children living in the slums.
The findings show the extent to which children resident in slums are underserved with vaccination and indicate that service delivery of immunization services in the urban slums needs to be reassessed to ensure that all children are reached.
PMCID: PMC3024932  PMID: 21205306
23.  Live Attenuated Influenza Vaccine, Trivalent, Is Safe in Healthy Children 18 Months to 4 Years, 5 to 9 Years, and 10 to 18 Years of Age in a Community-Based, Nonrandomized, Open-Label Trial 
Pediatrics  2005;116(3):e397-e407.
Influenza-associated deaths in healthy children that were reported during the 2003–2004 influenza season heightened the public awareness of the seriousness of influenza in children. In 1996–1998, a pivotal phase III trial was conducted in children who were 15 to 71 months of age. Live attenuated influenza vaccine, trivalent (LAIV-T), was shown to be safe and efficacious. In a subsequent randomized, double-blind, placebo-controlled LAIV-T trial in children who were 1 to 17 years of age, a statistically significant increase in asthma encounters was observed for children who were younger than 59 months. LAIV-T was not licensed to children who were younger than 5 years because of the concern for asthma. We report on the largest safety study to date of the recently licensed LAIV-T in children 18 months to 4 years, 5 to 9 years, and 10 to 18 years of age in a 4-year (1998–2002) community-based trial that was conducted at Scott & White Memorial Hospital and Clinic (Temple, TX).
An open-label, nonrandomized, community-based trial of LAIV-T was conducted before its licensure. Medical records of all children were surveyed for serious adverse events (SAEs) 6 weeks after vaccination. Health care utilization was evaluated by determining the relative risk (RR) of medically attended acute respiratory illness (MAARI) and asthma rates at 0 to 14 and 15 to 42 days after vaccination compared with the rates before vaccination. Medical charts of all visits coded as asthma were reviewed for appropriate classification of events: acute asthma or other. We evaluated the risk for MAARI (health care utilization for acute respiratory illness) 0 to 14 and 15 to 42 days after LAIV-T by a method similar to the postlicensure safety analysis conducted on measles, mumps, and rubella and on diphtheria, tetanus, and whole-cell pertussis vaccines.
All children regardless of age were administered a single intranasal dose of LAIV-T in each vaccine year. In the 4 years of the study, we administered 18 780 doses of LAIV-T to 11 096 children. A total of 4529, 7036, and 7215 doses of LAIV-T were administered to children who were 18 months to 4 years, 5 to 9 years, and 10 to 18 years of age, respectively. In vaccination years 1, 2, 3, and 4, we identified 10, 15, 11, and 6 SAEs, respectively. None of the SAEs was attributed to LAIV-T. In vaccination years 1, 2, 3, and 4, we identified 3, 2, 1, and 0 pregnancies, respectively, among adolescents. All delivered healthy infants. The RR for MAARI from 0 to 14 and 15 to 42 days after LAIV-T was assessed in vaccinees during the 4 vaccine years. Compared with the prevaccination period, there was no significant increase in risk in health care utilization attributed to MAARI from 0 to 14 and 15 to 42 days after vaccination in children who were 18 months to 4 years, 5 to 9 years, and 10 to 18 years of age in the 4 vaccine years. In children who were 18 months to 4 years of age, there was no significant increase in the risk in health care utilization for MAARI, MAARI subcategories (otitis media/sinusitis, upper respiratory tract illness, and lower respiratory tract illness), and asthma during the 0 to 14 days after vaccination compared with the prevaccination period. No significant increase in the risk in health care utilization for MAARI, MAARI subcategories, and asthma was detected when the risk period was extended to 15 to 42 days after vaccination, except for asthma events in vaccine year 1. A RR of 2.85 (95% confidence interval [CI]: 1.01–8.03) for asthma events was detected in children who were 18 months to 4 years of age but was not significantly increased for the other 3 vaccine years (vaccine year 2, RR: 1.42 [95% CI: 0.59–3.42]; vaccine year 3, RR: 0.47 [95% CI: 0.12–1.83]; vaccine year 4, RR: 0.20 [95% CI: 0.03–1.54]). No significant increase in the risk in health care utilization for MAARI or asthma was observed in children who were 18 months to 18 years of age and received 1, 2, 3, or 4 annual sequential doses of LAIV-T. Children who were 18 months to 4 years of age and received 1, 2, 3, or 4 annual doses of LAIV-T did not experience a significant increase in the RR for MAARI 0 to 14 days after vaccination; this was also true for children who were 5 to 9 and 10 to 18 years of age.
We observed no increased risk for asthma events 0 to 14 days after vaccination in children who were 18 months to 4 years, 5 to 9 years, and 10 to 18 years of age, In vaccine year 1, children who were 18 months to 4 years of age did have a significantly higher RR (2.85; 95% CI: 1.01–8.03) for asthma events 15 to 42 days after vaccination. In vaccine year 2, the formulation of LAIV-T was identical to the vaccine formulation used in vaccine year 1; however, in children who were 18 months to 4 years of age, no statistically significant increased risk was detected for asthma events 15 to 42 days after vaccination. Similarly, in vaccine years 3 and 4, children who were 18 months to 4 years of age did not have a statistically significant increased risk for asthma events 15 to 42 days after vaccination. Also, LAIV-T did not increase the risk for asthma in children who received 1, 2, 3, or 4 annual doses of LAIV-T. Although the possibility for a true increased risk for asthma was observed in 1 of 4 years in children who were 18 months to 4 years at 15 to 42 days after vaccination, it is more likely that the association is a chance effect because of the 190 comparisons made without adjustment for multiple comparisons. We conclude that LAIV-T is safe in children who are 18 months to 4 years, 5 to 9 years, and 10 to 18 years of age. The hypothesis that LAIV-T is associated with an increase in asthma events in children who are younger than 5 years is not supported by our data. Reassessment of the lower age limit for use of LAIV-T in children is indicated.
PMCID: PMC1361119  PMID: 16140685
asthma exacerbation; children and adolescents; health service utilization; influenza vaccine; outcome assessment; RSV, respiratory syncytial virus; LAIV-T, live attenuated influenza vaccine, trivalent; MAARI, medically attended acute respiratory illness; FDA, Food and Drug Administration; SAE, serious adverse event; SWHP, Scott & White Health Plan; RR, relative risk; ICD-9, International Classification of Diseases, Ninth Revision; CI, confidence interval
24.  The Measels-Mumps-Rubella Vaccination from a health political and economical point of view 
Measels, Mumps and Rubella (MMR) are highly contagious infectious diseases which may lead to severe complications. These diseases are vaccine-preventable. The present Health Technology Assessment report (report on technological consequences, HTA report) was commissioned by the German Institute of Medical Documentation and Information (DIMDI) and addresses various aspects of the MMR vaccination, the key question being how the MMR immunisation coverage rate can be increased in Germany.
The objectives of this report were to describe the benefits of the MMR vaccination for Germany and to analyse how the desired MMR immunisation coverage of >95% can be achieved.
A systematic literature search was performed in 29 literature data bases. Particularly for epidemiological data and information on vaccination programs, this systematic search was supplemented by an extensive hand search, written and oral enquiries, as well as interviews with experts. A total of 200 texts were used to prepare this report.
At 92.5% (as of 2004) based on the whole of Germany, the current immunisation coverage for measles in children is above the weighted EC-15-average of 90.67%. Statements can only be made regarding the probability of illness for measles, as no data is available for mumps and rubella. With 2.8 infections (per 100,000 residents) in 2006, Germany has not achieved the WHO target. Of cases submitted to the laboratory, only 32% were validated by diagnostic laboratory findings and 45% confirmed clinical-epidemiologically.
There are only few economic analyses of vaccination programs in Germany. In international publications, mainly measels are validated economically. An analysis of the cost of measles for Germany shows potential cost savings. Unfortunately, no complete economic evaluation (cost-effectiveness, cost-benefit, or cost-utility analyses) for MMR vaccination has been performed for Germany. Analyses conducted in the US and a model calculation for a hypothetical Western-European country show a considerable cost saving potential for society in general as well as for the health care system.
Interventions to increase the immunisation rate were categorized in three main groups according to their goals: interventions increasing the demand for vaccinations, those improving access to vaccination services and those aiming at the providers (e.g. physicians) of vaccinations.
Various studies concluded that reminders to clients, provided in written, electronic or oral form, are a highly recommendable intervention. Provider based interventions were also strongly advised.
Despite efforts made during the past years to achieve herd immunity in Germany, some deficits remain: i. e. there are still ample regional differences between and within German federal states.
In the authors’ opinion, a key point in increasing immunisation coverage is the development of a binding vaccination program for Germany with regionally differentiated immunisation targets. During the development of such a program, special emphasis should be placed on determining responsibilities of the federal government, the Laender and health insurance funds (e. g. in the case of a measles outbreak).
PMCID: PMC3011330  PMID: 21289946
25.  Immunization coverage and risk factors for failure to immunize within the Expanded Programme on Immunization in Kenya after introduction of new Haemophilus influenzae type b and hepatitis b virus antigens 
BMC Public Health  2006;6:132.
Kenya introduced a pentavalent vaccine including the DTP, Haemophilus influenzae type b and hepatitis b virus antigens in Nov 2001 and strengthened immunization services. We estimated immunization coverage before and after introduction, timeliness of vaccination and risk factors for failure to immunize in Kilifi district, Kenya.
In Nov 2002 we performed WHO cluster-sample surveys of >200 children scheduled for vaccination before or after introduction of pentavalent vaccine. In Mar 2004 we conducted a simple random sample (SRS) survey of 204 children aged 9–23 months. Coverage was estimated by inverse Kaplan-Meier survival analysis of vaccine-card and mothers' recall data and corroborated by reviewing administrative records from national and provincial vaccine stores. The contribution to timely immunization of distance from clinic, seasonal rainfall, mother's age, and family size was estimated by a proportional hazards model.
Immunization coverage for three DTP and pentavalent doses was 100% before and 91% after pentavalent vaccine introduction, respectively. By SRS survey, coverage was 88% for three pentavalent doses. The median age at first, second and third vaccine dose was 8, 13 and 18 weeks. Vials dispatched to Kilifi District during 2001–2003 would provide three immunizations for 92% of the birth cohort. Immunization rate ratios were reduced with every kilometre of distance from home to vaccine clinic (HR 0.95, CI 0.91–1.00), rainy seasons (HR 0.73, 95% CI 0.61–0.89) and family size, increasing progressively up to 4 children (HR 0.55, 95% CI 0.41–0.73).
Vaccine coverage was high before and after introduction of pentavalent vaccine, but most doses were given late. Coverage is limited by seasonal factors and family size.
PMCID: PMC1475578  PMID: 16707013

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