Age at pertussis immunization as it relates to current epidemiology and disease control

Decisions about vaccine use involve the risks of disease, efficacy of the vaccine, and adverse events associated with the vaccine. The goal is to provide protection at the earliest possible age. Available data suggest that even very young infants develop a protective response to a multi-dose series of pertussis vaccine. There are not conclusive data to indicate that true reactions to pertussis vaccine are age-related. The approach in the United States has been to recommend pertussis vaccination early in infancy, usually giving pertussis vaccine in combination with tetanus and diphtheria toxoids as DTP at 2, 4 and 6 months of age with a fourth dose at 15-18 months and a booster dose at 4-6 years just prior to school entry. In recent years, concern about adverse effects possibly caused by pertussis vaccine have led to suggestions that the administration of DTP be delayed by varying periods. To estimate the effects of a 6-month delay in the primary vaccination series, we conducted a decision analysis, following two hypothetical cohorts of 3.7 million children each from birth to their fourth birthday. One cohort was vaccinated at 2, 4, 6 and 18 months of age (the current schedule) whereas the other cohort was vaccinated at 8, 10, 12 and 18 months of age (the proposed schedule). Under base case conditions, assuming no change in adverse events attributable to DTP, a 6-month delay in initiating DTP vaccination would result in 636 more reported cases of pertussis, many with complications.(ABSTRACT TRUNCATED AT 250 WORDS)