After relative absence of Bordetella pertussis during the COVID-19 pandemic, notifications in the Netherlands were increased from May 2023 till September 2024. We monitored the largest pertussis outbreak in decades and investigated underlying immunological dynamics based on IgG and IgA antibodies against pertussis antigens (Ptx, FHA & Prn). We analyzed serum from 418 participants (2–87 years) at five timepoints (November 2022-October 2024) from a nationwide prospective serosurveillance study (PIENTER-Corona). Weighted incidence over two years was 6.3% (95% CI: 4.4-8.2) in the Dutch population, and 35% (95% CI: 26.2-44.6) in 6-18y-olds. Children aged 6-12 years, who received a booster vaccination at 4 years, showed lowest anti-Ptx IgG concentrations after the period of reduced circulation. Infected individuals had lower pre-infection anti-FHA IgG and IgA concentrations than matched uninfected individuals. Prolonged coughing was reported by 16% of the infected individuals. Our findings highlight the B. pertussis outbreak was preceded by waning immunity, particularly after acellular pertussis booster vaccination. The small proportion of symptomatic infections implies sufficient protection by the vaccine against disease but not transmission.
Gaasbeek et al. (Fri,) studied this question.