ANTIBODY-RESPONSES AND PERSISTENCE IN THE 2 YEARS AFTER IMMUNIZATION WITH 2 ACELLULAR VACCINES AND ONE WHOLE-CELL VACCINE AGAINST PERTUSSIS

Objective: To evaluate the persistence of specific antibodies induced by primary immunization with three doses of two three-component acellu lar vaccines against pertussis with an observed efficacy of 84%, and o ne whole-cell vaccine with an observed efficacy of 36%. Study design: Serum samples were collected from a subsample of 1572 children from th e Italian double-blind, placebo-controlled, randomized trial Of vaccin es used in 15,601 children at three time points: before administration of the first dose of vaccine, and 1 month and approximately 15 months after administration of the third dose. Further evaluation included p ooled cross-sectional analysis of serum specimens associated with epis odes of cough (which were not laboratory confirmed as pertussis infect ion) occurring among the entire population enrolled in the trial. Resu lts: With both acellular vaccines there was a fast and steep decrease in geometric mean antibody titers to pertussis toxin, filamentous hema gglutinin, and pertactin after vaccination. Mean titers were close to the limit of detection 15 months after primary immunization. The immun ogenicity of the whole-cell study vaccine was poor 1 month after the t hird dose, and no antibody was detected in nearly all children 15 mont hs after whole-cell vaccination. Conclusions: Although the study acell ular pertussis vaccines induced a strong primary specific antibody res ponse in almost all recipients, the duration of the response was limit ed. Sustained high-level production of antibody to the antigens tested does not account for the observed efficacy of acellular pertussis vac cines.