Herd immunity and pneumococcal conjugate vaccine: A quantitative model

Department of Biostatistics, Rollins School of Public Health, Emory University, Atlanta, GA 30322, USA.
Vaccine (Impact Factor: 3.62). 08/2007; 25(29):5390-8. DOI: 10.1016/j.vaccine.2007.04.088
Source: PubMed


Invasive pneumococcal disease in older children and adults declined markedly after introduction in 2000 of the pneumococcal conjugate vaccine for young children. An empirical quantitative model was developed to estimate the herd (indirect) effects on the incidence of invasive disease among persons ≥5 years of age induced by vaccination of young children with 1, 2, or ≥3 doses of the pneumococcal conjugate vaccine, Prevnar® (PCV7), containing serotypes 4, 6B, 9V, 14, 18C, 19F and 23F. From 1994 to 2003, cases of invasive pneumococcal disease were prospectively identified in Georgia Health District-3 (eight metropolitan Atlanta counties) by Active Bacterial Core surveillance (ABCs). From 2000 to 2003, vaccine coverage levels of PCV7 for children aged 19-35 months in Fulton and DeKalb counties (of Atlanta) were estimated from the National Immunization Survey (NIS). Based on incidence data and the estimated average number of doses received by 15 months of age, a Poisson regression model was fit, describing the trend in invasive pneumococcal disease in groups not targeted for vaccination (i.e., adults and older children) before and after the introduction of PCV7.

Download full-text


Available from: Walter A Orenstein,
  • Source
    • "Prior to this observation, surveillance carried out in the US demonstrated a 42 % fall in the incidence of IPD in infants ,90 days old (Carter, 2006), indicating that herd immunity can also extend to those not yet old enough to be vaccinated or to have completed the vaccination course. A US model also predicted that even incomplete coverage and/or limited dose schedules would still confer herd immunity (Haber et al., 2007). Herd immunity, primarily due to reduced exposure through decreased carriage and transmission from the vaccinated population, contributes extensively to the overall impact and cost-effectiveness of vaccination (CDC, 2005; Melegaro & Edmunds, 2004). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Streptococcus pneumoniae, also known as the pneumococcus, is an important cause of morbidity and mortality in the developed and developing world. Pneumococcal conjugate vaccines were first introduced for routine use in the USA in 2000, although the seven-valent pneumococcal conjugate vaccine (PCV7) was not introduced into the UK's routine childhood immunization programme until September 2006. After its introduction, a marked decrease in the incidence of pneumococcal disease was observed, both in the vaccinated and unvaccinated UK populations. However, pneumococci are highly diverse and serotype prevalence is dynamic. Conversely, PCV7 targets only a limited number of capsular types, which appears to confer a limited lifespan to the observed beneficial effects. Shifts in serotype distribution have been detected for both non-invasive and invasive disease reported since PCV7 introduction, both in the UK and elsewhere. The pneumococcal Haemophilus influenzae protein D conjugate vaccine (PHiD-CV, Synflorix; GlaxoSmithKline) and 13-valent pneumococcal conjugate vaccine (PCV13, Prevenar 13; Pfizer) have been newly licensed. The potential coverage of the 10- and 13-valent conjugate vaccines has also altered alongside serotype shifts. Nonetheless, the mechanism of how PCV7 has influenced serotype shift is not clear-cut as the epidemiology of serotype prevalence is complex. Other factors also influence prevalence and incidence of pneumococcal carriage and disease, such as pneumococcal diversity, levels of antibiotic use and the presence of risk groups. Continued surveillance and identification of factors influencing serotype distribution are essential to allow rational vaccine design, implementation and continued effective control of pneumococcal disease.
    Journal of Medical Microbiology 10/2010; 60(Pt 1):1-8. DOI:10.1099/jmm.0.020016-0 · 2.25 Impact Factor
  • Source
    • "However, to the best of the authors' knowledge, no mathematical epidemiologic model to characterize the indirect effect of infant PCV7 vaccination has yet been developed. The only study to estimate a measure of herd effect as a focal point of a quantitative model is that conducted by Haber and colleagues [11]. This group developed a Poisson regression model designed to predict the expected yearly incidence of IPD for several age groups using the mean number of doses per 15-month-old child as an explanative variable. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We developed an age-structured, transmission-dynamic, mathematical model to quantify the direct and indirect benefits of infant PCV7 vaccination. The model simulates the acquisition of asymptomatic carriage of Streptococcus pneumoniae and the development of fatal and non-fatal invasive pneumococcal disease (IPD) among vaccinated and unvaccinated individuals aged <2, 2-4, 5-17, 18-49, 50-64, and >or=65 years old. The model was parameterized using published US surveillance data, supplemented with data from published literature. The model predicts the observed incidence of IPD with good agreement and may be used to predict the impact of various vaccination strategies in the US or other populations yet to introduce PCV7.
    Vaccine 06/2009; 27(34):4694-703. DOI:10.1016/j.vaccine.2009.05.062 · 3.62 Impact Factor
  • Source

Show more