Figure 2.

Maternal vaccination with pertussis toxoid (PTx) vaccine prevents clinical signs and extreme leukocytosis in newborn baboons following infection with Bordetella pertussis. Infant baboons born to mothers vaccinated with the monocomponent PTx vaccine during pregnancy (PTx) or to unvaccinated mothers (Unv) were challenged with B. pertussis at 5–6 weeks of age. Daily health reports for each animal were reviewed by blinded researchers, and clinical scores were assigned independently, based on the following scale: 0, no disease; 1, mild disease; 2, severe disease; and 3, very severe disease (requiring euthanasia). A, The averages of the assigned clinical scores for each group are shown. B, The peak fold change in circulating white blood cell (WBC) counts relative to the prechallenge baseline counts are shown for each group of animals.