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Despite high immunization rates with pertussis vaccines, clinical cases of pertussis have resurged in the United States. In the 1990s, acellular pertussis (aP) vaccines replaced whole-cell pertussis (wP) vaccines because of toxicity concerns. To assess whether the increase in pertussis cases is related to relatively lower efficacy of aP vaccines, FDA researchers compared infant baboons who had been immunized using either an aP and or a wP vaccine (at 2, 4, and 6 months of age) with nonvaccinated animals and with previously infected convalescent animals. Each group included three or four baboons.
Vaccine-naive 7-month-old baboons challenged with Bordetella pertussis became heavily colonized, developed marked leukocytosis, and exhibited persis…