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1.  Validity of a reported history of chickenpox in targeting varicella vaccination at susceptible adolescents in England☆ 
Vaccine  2014;32(10):1213-1217.
Highlights
•Chickenpox history may enable cost-effective vaccination of susceptible individuals.•We tested the validity of reported chickenpox history in adolescents.•Vaccine would be wasted in most adolescents with a negative or uncertain history.•6–9% of those with a positive chickenpox history would remain susceptible.•These data are needed to inform cost-effectiveness of proposed vaccine programmes.
Introduction
In the UK, primary varicella is usually a mild infection in children, but can cause serious illness in susceptible pregnant women and adults. The UK Joint Committee on Vaccination and Immunisation is considering an adolescent varicella vaccination programme. Cost-effectiveness depends upon identifying susceptibles and minimising vaccine wastage, and chickenpox history is one method to screen for eligibility. To inform this approach, we estimated the proportion of adolescents with varicella antibodies by reported chickenpox history.
Methods
Recruitment occurred through secondary schools in England from February to September 2012. Parents were asked about their child's history of chickenpox, explicitly setting the context in terms of the implications for vaccination. 247 adolescents, whose parents reported positive (120), negative (77) or uncertain (50) chickenpox history provided oral fluid for varicella zoster virus-specific immunoglobulin-G (VZV-IgG) testing.
Results
109 (90.8% [85.6–96.0%]) adolescents with a positive chickenpox history, 52 (67.5% [57.0–78.1%]) with a negative history and 42 (84.0% [73.7–94.3%]) with an uncertain history had VZV-IgG suggesting prior infection. Combining negative and uncertain histories, 74% had VZV-IgG (best-case). When discounting low total-IgG samples and counting equivocals as positive (worst-case), 84% had VZV-IgG. We also modelled outcomes by varying the negative predictive value (NPV) for the antibody assay, and found 74–87% under the best-case and 84–92% under the worst-case scenario would receive vaccine unnecessarily as NPV falls to 50%.
Conclusion
Reported chickenpox history discriminates between varicella immunity and susceptibility in adolescents, but significant vaccine wastage would occur if this approach alone were used to determine vaccine eligibility. A small but important proportion of those with positive chickenpox history would remain susceptible. These data are needed to determine whether reported history, with or without oral fluid testing in those with negative and uncertain history, is sufficiently discriminatory to underpin a cost-effective adolescent varicella vaccination programme.
doi:10.1016/j.vaccine.2013.06.098
PMCID: PMC3969712  PMID: 23871823
Varicella; Chickenpox; Reported history; Validity; Adolescent; Vaccination programme
2.  Changes in Molecular Epidemiology of Streptococcus pneumoniae Causing Meningitis following Introduction of Pneumococcal Conjugate Vaccination in England and Wales 
Journal of Clinical Microbiology  2013;51(3):820-827.
The introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in September 2006 has markedly reduced the burden of invasive pneumococcal disease (IPD) including meningitis in England and Wales. This study examined changes in the molecular epidemiology of pneumococcal isolates causing meningitis from July 2004 to June 2009. The Health Protection Agency conducts enhanced pneumococcal surveillance in England and Wales. In addition to serotyping, pneumococcal isolates causing meningitis were genotyped by multilocus sequence typing (MLST). A total of 1,030 isolates were both serotyped and genotyped over the 5-year period. Fifty-two serotypes, 238 sequence types (STs), and 87 clonal complexes were identified, with no significant difference in the yearly Simpson's diversity index values (range, 0.974 to 0.984). STs commonly associated with PCV7 serotypes declined following PCV implementation, with a proportionally greater decline in ST124 (commonly associated with serotype 14). No other ST showed significant changes in distribution, even within individual serotypes. Replacement disease following PCV7 introduction was mainly due to serotypes 1, 3, 7F, 19A, 22F, and 33F through clonal expansion. A single instance of possible capsule switching was identified where one ST4327 clone expressed a serotype 14 capsule in 2005 and a serotype 28A capsule in 2009. In 2008 to 2009, ST191 (7F) became the most prevalent clone causing meningitis (10.3%). Case fatality (145 fatalities/1,030 cases; 14.1%) was high across all age groups and serotype groups. Thus, the introduction of PCV7 resulted in an increase in non-PCV7 serotypes, including some not covered by the 13-valent vaccine, such as serotypes 22F and 33F, emphasizing the importance of long-term epidemiological and molecular surveillance.
doi:10.1128/JCM.01917-12
PMCID: PMC3592052  PMID: 23269742
3.  Influenza and RSV make a modest contribution to invasive pneumococcal disease incidence in the UK 
The Journal of Infection  2013;66(6):512-520.
Summary
Objectives
The common seasonality of incidence of invasive pneumococcal disease (IPD) and viral respiratory infections has long been recognized, however, the extent to which this affects the association between the pathogens is unknown. We have analysed weekly surveillance data of IPD, influenza and respiratory syncytial virus (RSV), using ambient temperature and hours of sunshine as measures of seasonality.
Methods
Reported cases of influenza, IPD and RSV, were collected in England and Wales, from week 1 (January) 1996 to week 23 (June) 2009. The associations between IPD and respiratory viral infections were analysed using several statistical methods, including correlation coefficients and both additive and multiplicative regression models.
Results
6–7.5% of cases of IPD are attributable to influenza and 3–4% attributable to RSV. Correlation coefficients reported considerably stronger associations between IPD and the viral infections compared to regression models.
Conclusions
A small but potentially important percentage of IPD may be attributable to influenza and RSV when adjusted for seasonality by temperature. Jointly these viral infections may lead to over 10% of IPD cases. Therefore, prevention of viral respiratory infections may offer some additional benefit in reducing invasive pneumococcal infections.
doi:10.1016/j.jinf.2013.02.007
PMCID: PMC3650581  PMID: 23473714
Invasive pneumococcal disease; Influenza; Respiratory syncytial virus; Seasonality
4.  Invasive Pneumococcal Disease after Routine Pneumococcal Conjugate Vaccination in Children, England and Wales 
Emerging Infectious Diseases  2013;19(1):61-68.
Nonvaccine serotypes occur more often among children with comorbid conditions.
We assessed known risk factors, clinical presentation, and outcome of invasive pneumococcal disease (IPD) in children 3–59 months of age after introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in England and Wales. During September 2006–March 2010, a total of 1,342 IPD episodes occurred in 1,332 children; 14.9% (198/1,332) had comorbidities. Compared with IPD caused by PCV7 serotypes (44/248; 17.7%), comorbidities were less common for the extra 3 serotypes in the 10-valent vaccine (15/299; 5.0%) but similar to the 3 additional PCV13 serotypes (45/336; 13.4%) and increased for the 11 extra serotypes in 23-valent polysaccharide vaccine (PPV23) (39/186; 21.0%) and non-PPV23 serotypes (38/138; 27.5%). Fifty-two (3.9%) cases resulted from PCV7 failure; 9 (0.7%) case-patients had recurrent IPD. Case-fatality rate was 4.4% (58/1,332) but higher for meningitis (11.0%) and children with comorbidities (9.1%). Thus, comorbidities were more prevalent in children with IPD caused by non-PCV13 serotypes and were associated with increased case fatality.
doi:10.3201/eid1901.120741
PMCID: PMC3557991  PMID: 23259937
Invasive pneumococcal disease; risk factors; serotypes; meningitis; outcome; vaccination; bacteria; England; Wales; children
5.  Effect of Serotype on Focus and Mortality of Invasive Pneumococcal Disease: Coverage of Different Vaccines and Insight into Non-Vaccine Serotypes 
PLoS ONE  2012;7(7):e39150.
Background
Differences in pathogenicity between pneumococcal serotypes are important when assessing the potential benefit of different valency vaccines. We investigated the effect of serotype on clinical presentation, outcome, and quality of life lost from invasive pneumococcal disease (IPD) in the context of the 7, 10, and 13 valent pneumococcal conjugate vaccines (PCV7, PCV10, PCV13).
Method
Serotyped IPD cases in England were linked to the national dataset of hospital admissions for April 2002 to March 2011. Based on patients’ diagnostic codes and vital status at the end of the admission, disease focus (meningitis, empyema, sepsis, or respiratory disease) and case fatality rates by serotype and age group (5, 5–64, and 65 years and over) were obtained. Using these data the quality adjusted life years (QALY) lost from the IPD remaining when use of PCV7 stopped in 2010 was estimated for the serotypes covered by higher valency vaccines.
Results
The linked dataset contained 23,688 cases with information on diagnosis, mortality, and serotype. There were significant differences between serotypes in the propensity to cause meningitis, death, and QALY loss in each of the investigated age groups. As a result, vaccines’ coverage of disease burden differed by endpoint. For example, in children under 5 years in 2009/10, PCV10 covered 39% of meningitis, 19% of deaths and 28% of the QALY loss of attributable to IPD, whereas the respective percentages for PCV13 were 65%, 67%, and 66%. The highest QALY loss per serotype in this age group was for 6A. Non-PCV serotypes causing the highest QALY loss were 22F and 33F in <5 year olds and 31 in older individuals.
Conclusion
Marked differences exist between serotypes in clinical presentation and outcome, and these should be considered when evaluating the potential impact of higher valency vaccines on overall disease burden and associated QALY loss.
doi:10.1371/journal.pone.0039150
PMCID: PMC3398022  PMID: 22815698
6.  Pneumococcal Serotype–specific Unresponsiveness in Vaccinated Child with Cochlear Implant 
Emerging Infectious Diseases  2012;18(6):1024-1026.
doi:10.3201/eid1806.110906
PMCID: PMC3358141  PMID: 22607691
invasive pneumococcal disease; recurrent; cochlear implant; serotype hyporesponsiveness; pneumococcal conjugate vaccination; bacteria
7.  Placental malaria is associated with attenuated CD4 T-cell responses to tuberculin PPD 12 months after BCG vaccination 
Background
Placental malaria (PM) is associated with prenatal malaise, but many PM+ infants are born without symptoms. As malaria has powerful immunomodulatory effects, we tested the hypothesis that PM predicts reduced T-cell responses to vaccine challenge.
Methods
We recruited healthy PM+ and PM- infants at birth. At six and 12 months, we stimulated PBMCs with tuberculin purified protein derivative (PPD) and compared expression of CD154, IL-2 and IFNγ by CD4 T-cells to a negative control using flow cytometry.
We measured the length, weight and head circumference at birth and 12 months.
Results
IL-2 and CD154 expression were low in both groups at both timepoints, without discernable differences. Expression of IFNγ was similarly low at 6 months but by 12 months, the median response was higher in PM- than PM + infants (p = 0.026). The PM+ infants also had a lower weight (p = 0.032) and head circumference (p = 0.041) at 12 months, indicating lower growth rates.
At birth, the size and weight of the PM+ and PM- infants were equivalent. By 12 months, the PM+ infants had a lower weight and head circumference than the PM- infants.
Conclusions
Placental malaria was associated with reduced immune responses 12 months after immune challenge in infants apparently healthy at birth.
doi:10.1186/1471-2334-12-6
PMCID: PMC3274427  PMID: 22243970
8.  Using the Indirect Cohort Design to Estimate the Effectiveness of the Seven Valent Pneumococcal Conjugate Vaccine in England and Wales 
PLoS ONE  2011;6(12):e28435.
Background
The 7-valent pneumococcal conjugate vaccine (PCV-7) was introduced in the United Kingdom in 2006 with a 2,3 and 13month schedule, and has led to large decreases in invasive pneumococcal disease (IPD) caused by the vaccine serotypes in both vaccinated and unvaccinated cohorts. We estimated the effectiveness of PCV-7 against IPD.
Methods and Findings
We used enhanced surveillance data, collated at the Health Protection Agency, on vaccine type (n = 153) and non vaccine type (n = 919) IPD cases eligible for PCV-7. The indirect cohort method, a case-control type design which uses non vaccine type cases as controls, was used to estimate effectiveness of various numbers of doses as well as for each vaccine serotype. Possible bias with this design, caused by differential serotype replacement in vaccinated and unvaccinated individuals, was estimated after deriving formulae to quantify the bias. The results showed good effectiveness, increasing from 56% (95% confidence interval (CI): -7-82) for a single dose given under one year of age to 93% (95% CI: 70-98) for two doses under one year of age plus a booster dose in the second year of life. Serotype specific estimates indicated higher effectiveness against serotypes 4, 14 and 18C and lower effectiveness against 6B. Under the assumption of complete serotype replacement by non vaccine serotypes in carriage, we estimated that effectiveness estimates may be overestimated by about 2 to 5%.
Conclusions
This study shows high effectiveness of PCV-7 under the reduced schedule used in the UK. This finding agrees with the large reductions seen in vaccine type IPD in recent years in England and Wales. The formulae derived to assess the bias of the indirect cohort method for PCV-7 can also be used when using the design for other vaccines that affect carriage such as the recently introduced 13 valent pneumococcal conjugate vaccine.
doi:10.1371/journal.pone.0028435
PMCID: PMC3229580  PMID: 22164292
9.  7-Valent Pneumococcal Conjugate Vaccination in England and Wales: Is It Still Beneficial Despite High Levels of Serotype Replacement? 
PLoS ONE  2011;6(10):e26190.
Background
The UK introduced the 7-valent pneumococcal conjugate vaccine (PCV7) into the national vaccination program in September 2006. Previous modelling assumed that the likely impact of PCV7 on invasive pneumococcal disease (IPD) would be similar to the US experience with PCV7. However, recent surveillance data show a more rapid replacement of PCV7 IPD cases by non-PCV7 IPD cases than was seen in the US.
Methods and Findings
A previous model of pneumococcal vaccination was re-parameterised using data on vaccine coverage and IPD from England and Wales between 2006 and 2009. Disease incidence was adjusted for the increasing trend in reported IPD cases prior to vaccination. Using this data we estimated that individuals carrying PCV7 serotypes have much higher protection (96%;95% CI 72%-100%) against acquisition of NVT carriage than the 15% previously estimated from US data, which leads to greater replacement. However, even with this level of replacement, the annual number of IPD cases may be 560 (95% CI, -100 to 1230) lower ten years after vaccine introduction compared to what it may have been without vaccination. A particularly marked fall of 39% in children under 15 years by 2015/6 is predicted.
Conclusion
Our model suggests that PCV7 vaccination could result in a decrease in overall invasive pneumococcal disease, particularly in children, even in an environment of rapid replacement with non-PCV7 serotypes within 5 years of vaccine introduction at high coverage.
doi:10.1371/journal.pone.0026190
PMCID: PMC3193519  PMID: 22022559
10.  Safety and Immunogenicity of Coadministering a Combined Meningococcal Serogroup C and Haemophilus influenzae Type b Conjugate Vaccine with 7-Valent Pneumococcal Conjugate Vaccine and Measles, Mumps, and Rubella Vaccine at 12 Months of Age ▿  
The coadministration of the combined meningococcal serogroup C conjugate (MCC)/Haemophilus influenzae type b (Hib) vaccine with pneumococcal conjugate vaccine (PCV7) and measles, mumps, and rubella (MMR) vaccine at 12 months of age was investigated to assess the safety and immunogenicity of this regimen compared with separate administration of the conjugate vaccines. Children were randomized to receive MCC/Hib vaccine alone followed 1 month later by PCV7 with MMR vaccine or to receive all three vaccines concomitantly. Immunogenicity endpoints were MCC serum bactericidal antibody (SBA) titers of ≥8, Hib-polyribosylribitol phosphate (PRP) IgG antibody concentrations of ≥0.15 μg/ml, PCV serotype-specific IgG concentrations of ≥0.35 μg/ml, measles and mumps IgG concentrations of >120 arbitrary units (AU)/ml, and rubella IgG concentrations of ≥11 AU/ml. For safety assessment, the proportions of children with erythema, swelling, or tenderness at site of injection or fever or other systemic symptoms for 7 days after immunization were compared between regimens. No adverse consequences for either safety or immunogenicity were demonstrated when MCC/Hib vaccine was given concomitantly with PCV and MMR vaccine at 12 months of age or separately at 12 and 13 months of age. Any small differences in immunogenicity were largely in the direction of a higher response when all three vaccines were given concomitantly. For systemic symptoms, there was no evidence of an additive effect; rather, any differences between schedules showed benefit from the concomitant administration of all three vaccines, such as lower overall proportions with postvaccination fevers. The United Kingdom infant immunization schedule now recommends that these three vaccines may be offered at one visit at between 12 and 13 months of age.
doi:10.1128/CVI.00516-10
PMCID: PMC3067384  PMID: 21191076
11.  Effect of Pneumococcal Conjugate Vaccination on Serotype-Specific Carriage and Invasive Disease in England: A Cross-Sectional Study 
PLoS Medicine  2011;8(4):e1001017.
A cross sectional study by Stefan Flasche and coworkers document the serotype replacement of Streptococcus pneumoniae that has occurred in England since the introduction of PCV7 vaccination.
Background
We investigated the effect of the 7-valent pneumococcal conjugate vaccine (PCV7) programme in England on serotype-specific carriage and invasive disease to help understand its role in serotype replacement and predict the impact of higher valency vaccines.
Methods and Findings
Nasopharyngeal swabs were taken from children <5 y old and family members (n = 400) 2 y after introduction of PCV7 into routine immunization programs. Proportions carrying Streptococcus pneumoniae and serotype distribution among carried isolates were compared with a similar population prior to PCV7 introduction. Serotype-specific case∶carrier ratios (CCRs) were estimated using national data on invasive disease. In vaccinated children and their contacts vaccine-type (VT) carriage decreased, but was offset by an increase in non-VT carriage, with no significant overall change in carriage prevalence, odds ratio 1.06 (95% confidence interval 0.76–1.49). The lower CCRs of the replacing serotypes resulted in a net reduction in invasive disease in children. The additional serotypes covered by higher valency vaccines had low carriage but high disease prevalence. Serotype 11C emerged as predominant in carriage but caused no invasive disease whereas 8, 12F, and 22F emerged in disease but had very low carriage prevalence.
Conclusion
Because the additional serotypes included in PCV10/13 have high CCRs but low carriage prevalence, vaccinating against them is likely to significantly reduce invasive disease with less risk of serotype replacement. However, a few serotypes with high CCRs could mitigate the benefits of higher valency vaccines. Assessment of the effect of PCV on carriage as well as invasive disease should be part of enhanced surveillance activities for PCVs.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Pneumococcal diseases—major causes of illness and death in children and adults worldwide—are caused by Streptococcus pneumoniae, a bacterium that often colonizes the nasopharynx (the area of the throat behind the nose). Carriage of S. pneumoniae bacteria does not necessarily cause disease. However, these bacteria can cause local, noninvasive diseases such as ear infections and sinusitis and, more rarely, they can spread into the lungs, the bloodstream, or the covering of the brain, where they cause pneumonia, septicemia, and meningitis, respectively. Although these invasive pneumococcal diseases (IPDs) can be successfully treated if administered early, they can be fatal. Consequently, it is better to protect people against IPDs through vaccination than risk infection. Vaccination primes the immune system to recognize and attack disease-causing organisms (pathogens) rapidly and effectively by exposing it to weakened or dead pathogens or to pathogen molecules (antigens) that it recognizes as foreign.
Why Was This Study Done?
There are more than 90 S. pneumoniae variants or “serotypes” characterized by different polysaccharide (complex sugar) coats, which trigger the immune response against S. pneumoniae and determine each serotype's propensity to cause IPD. The pneumococcal conjugate vaccine PCV7 contains polysaccharides (linked to a protein carrier) from the seven serotypes mainly responsible for IPD in the US in 2000 when routine childhood PCV7 vaccination was introduced in that country. PCV7 prevents both IPD caused by the serotypes it contains and carriage of these serotypes, which means that, after vaccination, previously uncommon, nonvaccine serotypes can colonize the nasopharynx. If these serotypes have a high invasiveness potential, then “serotype replacement” could reduce the benefits of vaccination. In this cross-sectional study (a study that investigates the relationship between a disease and an intervention in a population at one time point), the researchers investigate the effect of the UK PCV7 vaccination program (which began in 2006) on serotype-specific carriage and IPD in England to understand the role of PCV7 in serotype replacement and to predict the likely impact of vaccines containing additional serotypes (higher valency vaccines).
What Did the Researchers Do and Find?
The researchers examined nasopharyngeal swabs taken from PCV7-vaccinated children and their families for S. pneumoniae, determined the serotype of any bacteria they found, and compared the proportion of people carrying S. pneumoniae (carrier prevalence) and the distribution of serotypes in this study population and in a similar population that was studied in 2000/2001, before the PCV vaccination program began. Overall, there was no statistically significant change in carrier prevalence, but carriage of vaccine serotypes decreased in vaccinated children and their contacts whereas carriage of nonvaccine serotypes increased. The serotype-specific case-to-carrier ratios (CCRs; a measure of serotype invasiveness that was estimated using national IPD data) of the replacing serotypes were generally lower than those of the original serotypes, which resulted in a net reduction in IPD in children. Moreover, before PCV7 vaccination began, PCV7-included serotypes were responsible for similar proportions of pneumococcal carriage and disease; afterwards, the additional serotypes present in the higher valency vaccines PVC10 and PVC13 were responsible for a higher proportion of disease than carriage. Finally, three serotypes not present in the higher valency vaccines with outstandingly high CCRs (high invasiveness potential) are identified.
What Do These Findings Mean?
These findings document the serotype replacement of S. pneumoniae that has occurred in England since the introduction of PCV7 vaccination and highlight the importance of assessing the effects of pneumococcal vaccines on carriage as well as on IPDs. Because the additional serotypes included in PCV10 and PCV13 have high CCRs but low carriage prevalence and because most of the potential replacement serotypes have low CCRs, these findings suggest that the introduction of higher valency vaccines should further reduce the occurrence of invasive disease with limited risk of additional serotype replacement. However, the emergence of a few serotypes that have high CCRs but are not included in PCV10 and PCV13 might mitigate the benefits of higher valency vaccines. In other words, although the recent introduction of PCV13 into UK vaccination schedules is likely to have an incremental benefit on the reduction of IPD compared to PCV7, this benefit might be offset by increases in the carriage of some high CCR serotypes. These serotypes should be considered for inclusion in future vaccines.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001017.
The US Centers for Disease Control and Prevention provides information for patients and health professionals on all aspects of pneumococcal disease and pneumococcal vaccination
The US National Foundation for Infectious Diseases has a fact sheet on pneumococcal diseases
The UK Health Protection Agency provides information on pneumococcal disease and on pneumococcal vaccines
The World Health Organization also provides information on pneumococcal vaccines
MedlinePlus has links to further information about pneumococcal infections (in English and Spanish)
doi:10.1371/journal.pmed.1001017
PMCID: PMC3071372  PMID: 21483718
14.  Age-Specific Incidence of A/H1N1 2009 Influenza Infection in England from Sequential Antibody Prevalence Data Using Likelihood-Based Estimation 
PLoS ONE  2011;6(2):e17074.
Estimating the age-specific incidence of an emerging pathogen is essential for understanding its severity and transmission dynamics. This paper describes a statistical method that uses likelihoods to estimate incidence from sequential serological data. The method requires information on seroconversion intervals and allows integration of information on the temporal distribution of cases from clinical surveillance. Among a family of candidate incidences, a likelihood function is derived by reconstructing the change in seroprevalence from seroconversion following infection and comparing it with the observed sequence of positivity among the samples. This method is applied to derive the cumulative and weekly incidence of A/H1N1 pandemic influenza in England during the second wave using sera taken between September 2009 and February 2010 in four age groups (1–4, 5–14, 15–24, 25–44 years). The highest cumulative incidence was in 5–14 year olds (59%, 95% credible interval (CI): 52%, 68%) followed by 1–4 year olds (49%, 95% CI: 38%, 61%), rates 20 and 40 times higher respectively than estimated from clinical surveillance. The method provides a more accurate and continuous measure of incidence than achieved by comparing prevalence in samples grouped by time period.
doi:10.1371/journal.pone.0017074
PMCID: PMC3044152  PMID: 21373639
15.  Age-Specific Effectiveness of an Oil-in-Water Adjuvanted Pandemic (H1N1) 2009 Vaccine Against Confirmed Infection in High Risk Groups in England 
Background. The use of a squalene-containing (AS03) pandemic vaccine for high-risk groups in England allowed vaccine effectiveness (VE) of such novel oil-in-water adjuvanted vaccine to be evaluated.
Methods. Cases of laboratory-confirmed pandemic (H1N1)2009 influenza in England between November 2009 and January 2010 were followed up for history of pandemic (H1N1)2009 or 2009/10 seasonal influenza vaccination and relevant comorbidities. Controls were patients similarly tested but negative for the virus. We estimated pandemic (H1N1)2009 VE from the relative reduction in the odds of confirmed pandemic (H1N1)2009 infection between vaccinated and unvaccinated individuals after adjustment for confounders.
Results. A total of 933 cases and 1220 controls were analyzed. VE from ≥14 days was 62% (95% CI 33% to 78%) with protection from 7 to 13 days post-vaccination (59%, 95% CI 12% to 81%). VE from ≥14 days differed by age (P=.03) being 77% (11% to 94%) in children <10 years, 100% (80% to 100%) in 10–24-year olds, 22% (-153% to 76%) in 25–49-year olds, and 41% (-71% to 80%) in 50-plus-year-olds.
Conclusion. Use of oil-in-water adjuvant contributed to a high VE with reduced antigen dosage in children and young adults. Our VE estimate supports the serological correlates of protection used for licensure in these age groups. However, the immunological basis of disappointing VE in older adults merits investigation.
doi:10.1093/infdis/jiq014
PMCID: PMC3086445  PMID: 21148494
16.  Epstein-Barr Virus but Not Cytomegalovirus Is Associated with Reduced Vaccine Antibody Responses in Gambian Infants 
PLoS ONE  2010;5(11):e14013.
Background
Epstein-Barr virus (EBV) and cytomegalovirus (CMV) are persistent herpesviruses that have various immunomodulatory effects on their hosts. Both viruses are usually acquired in infancy in Sub-Saharan Africa, a region where childhood vaccines are less effective than in high income settings. To establish whether there is an association between these two observations, we tested the hypothesis that infection with one or both viruses modulate antibody responses to the T-cell independent meningococcal polysaccharide vaccine and the T-cell dependent measles vaccines.
Methodology/Principal Findings
Infection with EBV and CMV was diagnosed by the presence of virus-specific IgM in the peripheral blood or by the presence of IgG at higher levels than that found in umbilical cord blood. Anti-meningococcus IgG and IgM were quantified by ELISA. Anti-measles antibody responses were quantified by haemagglutinin antibody inhibition assay. Infants infected with EBV had reduced IgG and IgM antibody responses to meningococcal polysaccharides and to measles vaccine. Infection with CMV alone predicted no changes in the response to meningococcal polysaccharide. While CMV alone had no discernable effect on the antibody response to measles, the response of infants infected with both CMV and EBV was similar to that of infants infected with neither, suggesting that the effects of CMV infection countered the effects of EBV on measles antibody responses.
Conclusions
The results of this exploratory study indicate that infection with EBV is associated with reduced antibody responses to polysaccharides and to measles vaccine, but suggest that the response to T-cell dependent antigens such as measles haemagglutinin may be restored by infection with CMV.
doi:10.1371/journal.pone.0014013
PMCID: PMC2984441  PMID: 21103338
17.  Host Genetic Factors and Vaccine-Induced Immunity to HBV Infection: Haplotype Analysis 
PLoS ONE  2010;5(8):e12273.
Hepatitis B virus (HBV) infection remains a significant health burden world-wide, although vaccines help decrease this problem. We previously identified associations of single nucleotide polymorphisms in several candidate genes with vaccine-induced peak antibody level (anti-HBs), which is predictive of long-term vaccine efficacy and protection against infection and persistent carriage; here we report on a haplotype-based analysis. A total of 688 SNPs from 117 genes were examined for a two, three and four sliding window haplotype analysis in a Gambian cohort. Analysis was performed on 197 unrelated individuals, 454 individuals from 174 families, and the combined sample (N = 651). Global and individual haplotype association tests were carried out (adjusted for covariates), employing peak anti-HBs level as outcome. Five genes (CD44, CD58, CDC42, IL19 and IL1R1) had at least one significant haplotype in the unrelated or family analysis as well as the combined analysis. Previous single locus results were confirmed for CD44 (combined global p = 9.1×10−5 for rs353644-rs353630-rs7937602) and CD58 (combined global p = 0.008 for rs1414275-rs11588376-rs1016140). Haplotypes in CDC42, IL19 and IL1R1 also associated with peak anti-HBs level. We have identified strong haplotype effects on HBV vaccine-induced antibody level in five genes, three of which, CDC42, IL19 and IL1R1, did not show evidence of association in a single SNP analyses and corroborated the majority of these effects in two datasets. The haplotype analysis identified associations with HBV vaccine-induced immunity in several new genes.
doi:10.1371/journal.pone.0012273
PMCID: PMC2923624  PMID: 20806065
18.  Kinetics of Antibody Persistence following Administration of a Combination Meningococcal Serogroup C and Haemophilus influenzae Type b Conjugate Vaccine in Healthy Infants in the United Kingdom Primed with a Monovalent Meningococcal Serogroup C Vaccine ▿  
The kinetics of antibody persistence following the administration of a combination meningococcal serogroup C and Haemophilus influenzae type b (Hib) conjugate vaccine (Menitorix) in the second year of life in children primed with two doses of one of three monovalent meningococcal serogroup C (MCC) vaccines was investigated. The study subjects were administered either Menitorix at 12 to 15 months of age, followed by the seven-valent pneumococcal conjugate vaccine (PCV7) and the measles, mumps, and rubella vaccine 4 to 6 weeks later, or all three vaccines concomitantly at 12 to 15 months of age. Blood samples were collected before and 1, 2, 12, and 24 months after the boosting. Sera were analyzed for meningococcal serogroup C serum bactericidal antibody (SBA) and IgG as well as Hib-polyribosylribitol phosphate (PRP)-specific IgG. The antibody persistence data from this study were compared to those of a prior study of Southern et al. (Clin. Vaccine Immunol. 14:1328-1333, 2007) in which children were given three primary doses of a vaccine containing both the MCC and the Hib vaccines but were boosted only with a Hib conjugate vaccine. The magnitude of the meningococcal SBA geometric mean titer was higher for those subjects primed with the MCC vaccine conjugated to tetanus toxoid (NeisVac-C) than for those primed with one of two MCC vaccines conjugated to CRM197 (Menjugate or Meningitec) up to 1 year following boosting. Two years after boosting, the percentages of subjects with putatively protective SBA titers of ≥8 for children primed with NeisVac-C, Menjugate, and Meningitec were 43%, 22%, and 23%, respectively. Additional booster doses of the MCC vaccine may be required in the future to maintain good antibody levels; however, there is no immediate need for a booster during adolescence, as mathematical modeling has shown that persisting herd immunity is likely to control disease for a number of years.
doi:10.1128/CVI.00384-09
PMCID: PMC2812092  PMID: 19906895
19.  Placental Malaria is associated with reduced early life weight development of affected children independent of low birth weight 
Malaria Journal  2010;9:16.
Background
Infection with Plasmodium falciparum during pregnancy contributes substantially to the disease burden in both mothers and offspring. Placental malaria may lead to intrauterine growth restriction or preterm delivery resulting in low birth weight (LBW), which, in general, is associated with increased infant morbidity and mortality. However, little is known about the possible direct impact of the specific disease processes occurring in PM on longer term outcomes such as subsequent retarded growth development independent of LBW.
Methods
In an existing West-African cohort, 783 healthy infants with a birth weight of at least 2,000 g were followed up during their first year of life. The aim of the study was to investigate if Plasmodium falciparum infection of the placenta, assessed by placental histology, has an impact on several anthropometric parameters, measured at birth and after three, six and 12 months using generalized estimating equations models adjusting for moderate low birth weight.
Results
Independent of LBW, first to third born infants who were exposed to either past, chronic or acute placental malaria during pregnancy had significantly lower weight-for-age (-0.43, 95% CI: -0.80;-0.07), weight-for-length (-0.47, 95% CI: -0.84; -0.10) and BMI-for-age z-scores (-0.57, 95% CI: -0.84; -0.10) compared to infants born to mothers who were not diagnosed with placental malaria (p = 0.019, 0.013, and 0.012, respectively). Interestingly, the longitudinal data on histology-based diagnosis of PM also document a sharp decline of PM prevalence in the Sukuta cohort from 16.5% in 2002 to 5.4% in 2004.
Conclusions
It was demonstrated that PM has a negative impact on the infant's subsequent weight development that is independent of LBW, suggesting that the longer term effects of PM have been underestimated, even in areas where malaria transmission is declining.
doi:10.1186/1475-2875-9-16
PMCID: PMC2841609  PMID: 20074331
20.  Monitoring the emergence of community transmission of influenza A/H1N1 2009 in England: a cross sectional opportunistic survey of self sampled telephone callers to NHS Direct 
Objective To evaluate ascertainment of the onset of community transmission of influenza A/H1N1 2009 (swine flu) in England during the earliest phase of the epidemic through comparing data from two surveillance systems.
Design Cross sectional opportunistic survey.
Study samples Results from self samples by consenting patients who had called the NHS Direct telephone health line with cold or flu symptoms, or both, and results from Health Protection Agency (HPA) regional microbiology laboratories on patients tested according to the clinical algorithm for the management of suspected cases of swine flu.
Setting Six regions of England between 24 May and 30 June 2009.
Main outcome measure Proportion of specimens with laboratory evidence of influenza A/H1N1 2009.
Results Influenza A/H1N1 2009 infections were detected in 91 (7%) of the 1385 self sampled specimens tested. In addition, eight instances of influenza A/H3 infection and two cases of influenza B infection were detected. The weekly rate of change in the proportions of infected individuals according to self obtained samples closely matched the rate of increase in the proportions of infected people reported by HPA regional laboratories. Comparing the data from both systems showed that local community transmission was occurring in London and the West Midlands once HPA regional laboratories began detecting 100 or more influenza A/H1N1 2009 infections, or a proportion positive of over 20% of those tested, each week.
Conclusions Trends in the proportion of patients with influenza A/H1N1 2009 across regions detected through clinical management were mirrored by the proportion of NHS Direct callers with laboratory confirmed infection. The initial concern that information from HPA regional laboratory reports would be too limited because it was based on testing patients with either travel associated risk or who were contacts of other influenza cases was unfounded. Reports from HPA regional laboratories could be used to recognise the extent to which local community transmission was occurring.
doi:10.1136/bmj.b3403
PMCID: PMC2733951  PMID: 19713236
21.  Immunogenicity of a Reduced Schedule of Meningococcal Group C Conjugate Vaccine Given Concomitantly with the Prevenar and Pediacel Vaccines in Healthy Infants in the United Kingdom▿  
This study investigated the use of two doses of three different meningococcal group C conjugate (MCC) vaccines when given for primary immunization with a seven-valent pneumococcal conjugate vaccine (PCV7) and Pediacel, a combination product containing five acellular pertussis components, diphtheria and tetanus toxoids, Haemophilus influenzae type b (Hib) conjugate, and inactivated-poliovirus vaccine. The immune response after a single dose of MCC is also presented. Infants were randomized to receive two doses of one of the MCC vaccines and PCV7 at 2 and 3 months or at 2 and 4 months of age. Meningococcal group C serum bactericidal antibody (SBA) geometric mean titers, Hib-polyribosylribitol phosphate (PRP) immunoglobulin G (IgG) geometric mean concentrations (GMCs), and diphtheria and tetanus antitoxin GMCs, together with the proportions of infants achieving putative protective levels, were determined. A total of 393 infants were recruited. Following the first dose of NeisVac-C (MCC conjugated to tetanus toxoid), 97% of infants achieved protective levels (SBA titer of ≥8), compared with 80% and 53%, respectively, for Menjugate and Meningitec (both of which are conjugated to CRM197). SBA responses to MCC vaccines were not significantly different when administered at 2 and 3 or 2 and 4 months of age. Following two doses of each MCC, 98 to 100% of infants achieved protective levels. Both PRP IgG and tetanus responses were significantly enhanced when Pediacel was coadministered with NeisVac-C. This study demonstrates that NeisVac-C and Menjugate generate good immunogenicity after the first dose at 2 months of age when coadministered with PCV7 and Pediacel and merit further investigation in single-dose priming strategies.
doi:10.1128/CVI.00420-08
PMCID: PMC2643544  PMID: 19091990
22.  Serotype-Specific Immune Unresponsiveness to Pneumococcal Conjugate Vaccine following Invasive Pneumococcal Disease▿  
Infection and Immunity  2008;76(11):5305-5309.
Following the introduction of the pneumococcal 7-valent conjugate vaccine (PCV7) into the routine infant immunization schedule in England, Wales, and Northern Ireland, pneumococcal serotype-specific immunoglobulin G (IgG) antibody testing was offered as a clinical service to all children within the program with invasive pneumococcal disease (IPD) to confirm an adequate antibody response to PCV7. As of March 2008, serum samples taken within 14 to 90 days of vaccination had been submitted from 107 children who had received one or more doses in the second year of life. Sera were assayed by a multiplexed microsphere assay incorporating both cell wall polysaccharide and serotype 22F adsorption. A protective serotype-specific antibody level was defined as a concentration of ≥0.35 μg/ml. Eight children failed to develop a response to their infecting serotype (6B [n = 4], 18C [n = 2], 4 [n = 1], and 14 [n = 1]), despite receiving at least three doses of PCV7 in the second year of life or two doses in the second and two or three in the first year of life. A further two children were nonresponsive to a serotype (6B) different than that causing disease. None of the 10 children had a clinical risk factor for IPD. Two had marginally low levels of total serum IgG but mounted adequate responses to the other six PCV serotypes. This serotype-specific unresponsiveness may reflect immune paralysis due to large pneumococcal polysaccharide antigen loads and/or a potential genetic basis for nonresponse to individual pneumococcal serotypes.
doi:10.1128/IAI.00796-08
PMCID: PMC2573380  PMID: 18779338
23.  Maintenance of Large Subpopulations of Differentiated CD8 T-Cells Two Years after Cytomegalovirus Infection in Gambian Infants 
PLoS ONE  2008;3(8):e2905.
Background
In a previously published study, we found that large differentiated subpopulations of CD8 T-cells emerged rapidly after CMV infection in young infants and persisted throughout the following year. Here we describe a follow-up study conducted on the same infants to establish whether the differentiated subpopulations continued through the second year post-infection.
Methodology / Principal Findings
CMV-specific cells identified using tetramers remained more activated and differentiated than the overall CD8 population. The large subpopulation of differentiated cytotoxic (CD28−CD62L−Bcl-2lowCD95+perforin+) cells that emerged rapidly after infection remained stable after two years. No similar subpopulation was found in CMV-uninfected infants indicating that two years after infection, CMV remained a major factor in driving CD8 T-cell differentiation. Although markers of activation (CD45R0 and HLA-D) declined throughout the first year, HLA-D expression continued to decline during the second year and CD45R0 expression increased slightly. The age-related increase in IFNγ response observed during the first year continued but was non-significant during the second year, indicating that the rate of functional improvement had slowed substantially.
Conclusions / Significance
The large differentiated subpopulations of CD8 T-cells that had emerged immediately after CMV infection persisted through the second year post-infection, while levels of activation and functional capacity remained fairly constant.
doi:10.1371/journal.pone.0002905
PMCID: PMC2483415  PMID: 18682836
24.  Host Genetic Factors and Vaccine-Induced Immunity to Hepatitis B Virus Infection 
PLoS ONE  2008;3(3):e1898.
Background
Vaccination against hepatitis B virus infection (HBV) is safe and effective; however, vaccine-induced antibody level wanes over time. Peak vaccine-induced anti-HBs level is directly related to antibody decay, as well as risk of infection and persistent carriage despite vaccination. We investigated the role of host genetic factors in long-term immunity against HBV infection based on peak anti-HBs level and seroconversion to anti-HBc.
Methods
We analyzed 715 SNP across 133 candidate genes in 662 infant vaccinees from The Gambia, assessing peak vaccine-induced anti-HBs level and core antibody (anti-HBc) status, whilst adjusting for covariates. A replication study comprised 43 SNPs in a further 393 individuals.
Results
In our initial screen we found variation in IFNG, MAPK8, and IL10RA to affect peak anti-HBs level (GMTratio of <0.6 or >1.5 and P≤0.001) and lesser associations in other genes. Odds of core-conversion was associated with variation in CD163. A coding change in ITGAL (R719V) with likely functional relevance showed evidence of association with increased peak anti-HBs level in both screens (1st screen: s595_22 GMTratio 1.71, P = 0.013; 2nd screen: s595_22 GMTratio 2.15, P = 0.011).
Conclusion
This is to our knowledge the largest study to date assessing genetic determinants of HBV vaccine-induced immunity. We report on associations with anti-HBs level, which is directly related to durability of antibody level and predictive of vaccine efficacy long-term. A coding change in ITGAL, which plays a central role in immune cell interaction, was shown to exert beneficial effects on induction of peak antibody level in response to HBV vaccination. Variation in this gene does not appear to have been studied in relation to immune responses to viral or vaccine challenges previously. Our findings suggest that genetic variation in loci other than the HLA region affect immunity induced by HBV vaccination.
doi:10.1371/journal.pone.0001898
PMCID: PMC2268746  PMID: 18365030
25.  Age-Stratified Prevalences of Pneumococcal-Serotype-Specific Immunoglobulin G in England and Their Relationship to the Serotype-Specific Incidence of Invasive Pneumococcal Disease Prior to the Introduction of the Pneumococcal 7-Valent Conjugate Vaccine▿  
Clinical and Vaccine Immunology : CVI  2007;14(11):1442-1450.
Recent changes to the childhood immunization schedule in the United Kingdom have resulted in the inclusion of the 7-valent pneumococcal conjugate vaccine. However, the seroprevalence of pneumococcal antibodies in the population was unknown. To address this, we measured pneumococcal, age-specific immunoglobulin G (IgG) concentrations specific for nine serotypes by an assay run on the Bioplex platform, using 2,664 serum samples collected in England from 2000 to 2004. The lowest concentrations of IgG specific to all serotypes and the proportions of serotype-specific IgG concentrations of ≥0.35 μg/ml were observed in children aged <1 year. From 1 year on, there was a general increase in antibody levels with increasing age, and they remained high in adults. Maternal antibody was detected in young children aged <36 days but waned rapidly. Comparison of the age-specific seroprevalence of serotype-specific IgG to the serotype-specific incidence of invasive pneumococcal disease demonstrated a general inverse relationship for all age groups except the elderly. These data provide a baseline for natural immunity to the pneumococcal serotypes analyzed prior to the introduction of pneumococcal conjugate vaccine in the United Kingdom.
doi:10.1128/CVI.00264-07
PMCID: PMC2168168  PMID: 17881503

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