Longitudinal assessment of asymptomatic infection of Bordetella pertussis among pertussis acellular vaccinated adolescents.

BACKGROUND

Recent animal model data suggest that acellular pertussis (aP) vaccines do not prevent asymptomatic Bordetella pertussis infection. We conducted a longitudinal study among a convenience sample of adolescents during the latter part of an outbreak to estimate the prevalence of B. pertussis asymptomatic infection and describe the associated serologic response in an aP-vaccinated population.

METHODS

From October-December 2019, we enrolled a convenience sample of adolescent students during a high school-based outbreak; a subset of participants was followed over a 6-week period. Epidemiologic and symptom data were collected at 3 separate time points (study rounds) each separated by 3 weeks; specimens (nasopharyngeal aspirates, blood) were collected at the first 2 study rounds. Nasopharyngeal aspirates were tested for B. pertussis by culture and real-time polymerase chain reaction (RT-PCR); serum was tested for IgG anti-pertussis toxin antibody (anti-PT). Asymptomatic infection was defined as B. pertussis laboratory-confirmation (RT-PCR or culture) during at least one study round in an asymptomatic participant who remained asymptomatic at the subsequent round.

RESULTS

The study included 534 participants; 75.3% had received only aP vaccines as children, and 100% received an adolescent booster. Fifteen participants were laboratory-confirmed for B. pertussis at ≥1 round. Nine of 15 participants remained asymptomatic at the subsequent study round resulting in an asymptomatic infection prevalence of 1.7%. Of the nine participants with asymptomatic B. pertussis infection, one (11%) was seropositive for anti-PT IgG.

DISCUSSION: We detected a low prevalence of B. pertussis asymptomatic infection among an aP-vaccinated adolescent population, with variable antibody response. While follow-up studies are needed, this information could help inform public health prevention strategies and development of new pertussis vaccines.