Primary immunization series for infants: comparison of two-component acellular and standard whole-cell pertussis vaccines combined with diphtheria-tetanus toxoids.

At 2 months of age, 145 infants were randomized to receive either a two-component acellular pertussis vaccine [lymphocytosis-promoting factor (LPF)/filamentous hemagglutinin (FHA)] or standard whole-cell pertussis vaccine, each combined with diphtheria-tetanus toxoids, as their primary immunization series. Of the 132 subjects (91%) who completed the study, those receiving the acellular vaccine had significantly fewer adverse reactions: 5% vs 30% (local) and 17% vs 30% (systemic, including fever). During the first 24 hours acetaminophen usage, a general measure of adverse reactions, was lower in the test group. Overall, 35% of the acellular vaccine doses were reaction free vs 12% of the whole-cell doses. No serious reactions occurred in either group. Antibody responses to LPF and to FHA were significantly increased after the second and third immunizations with the test vaccine and were consistently higher than levels achieved with the standard vaccine. Thus the two-component acellular pertussis vaccine was associated with fewer adverse reactions and improved serologic responses to LPF and FHA as compared with the currently recommended whole-cell vaccine.