Richard T. Ellison III, MD

The acellular pertussis vaccine protects infant baboons against disease but doesn't prevent colonization and transmission.

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 persistent colonization for 30 days. In contrast, none of the animals that had been immunized with either the wP or the aP vaccine, or that had experienced prior infection, showed signs of disease or developed leukocytosis. B. pertussis did not colonize convalescent baboons, but it did colonize those immunized with the wP vaccine (for a mean of 18 days) and those immunized with the aP vaccine (for a mean of 35 days).

Recipients of the aP vaccine that were colonized with B. pertussis could transmit infection to naive animals. Antibody titers against four aP vaccine antigens were comparable between the convalescent animals and the recipients of either the aP or the wP vaccine. However, convalescent animals and wP vaccine recipients had strong B. pertussis–specific T helper 17 (Th 17) memory and Th 1 memory responses, whereas aP vaccine recipients had a Th 1/Th 2 response.

CITATION(S):

Warfel JM et al. Acellular pertussis vaccines protect against disease but fail to prevent infection and transmission in a nonhuman primate model. Proc Natl Acad Sci U S A 2013 Nov 25; [e-pub ahead of print].