Fig. 2

Outcomes of experimental exposure to pertussis among aP or wP vaccinated or unvaccinated infant baboons. Three groups of infant baboons were exposed to infectious aerosols of B. pertussis: unvaccinated control animals; animals vaccinated using acellular pertussis vaccines; animals vaccinated using whole cell pertussis vaccines. The vaccinated animals completed a full vaccination series and were allowed time to fully seroconvert before exposure. The two vaccinated groups of animals both remained asymptomatic, whereas the unvaccinated animals developed clinical disease. However, nasopharyngeal sampling of the three groups showed that the aP and unvaccinated animals both were infected with similar densities of pertussis bacteria and for similar durations. By contrast, the wP vaccinated animals were more resistant to carriage, and carried bacteria for shorter periods. This showed that wP and aP vaccinations induce very different mucosal immune responses, with the former protecting against infection and disease, and the latter only preventing clinical disease, but not infection