Article

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: 3.49). 08/2007; 25(29):5390-8. DOI: 10.1016/j.vaccine.2007.04.088
Source: PubMed

ABSTRACT 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.

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