Convalescence from a symptomatic B. pertussis infection induces long-lasting protection against future B. pertussis colonization and whooping cough. In contrast, researchers from the FDA have demonstrated, in a nonhuman primate model, that the aP vaccine currently administered in the U.S. and other developed countries does not prevent B. pertussis colonization nor transmission to a co-located animal. These results are corroborated by human epidemiological studies from around the world that show subclinical B. pertussis infection rates from 5% - 14% in highly aP vaccinated populations. The public health concern is that these subclinically colonized individuals can transmit B. pertussis to vulnerable infants, especially those younger than 6 months of age.
Further supporting the need to address subclinical B. pertussis colonization infections, mathematical and computational models have shown asymptomatic transmission of B. pertussis to be the most critical factor explaining the resurgence of pertussis in the U.S. – more impactful than low vaccination rates, waning aP protective immunity, or the evolution of B. pertussis strains.