Understanding the Epidemiology and Contributing Factors of Post-COVID-19 Pertussis Outbreaks: A Narrative Review.

Pertussis or whooping cough, caused by the bacteria Bordetella pertussis, is a highly contagious respiratory disease. Over the past century, whole-cell pertussis (wP) and acellular pertussis (aP) vaccines were developed and widely adopted, leading to a substantial reduction in the number of pertussis cases. Currently, various strategies are employed to protect different segments of the population, including primary immunization, toddler and school-age boosters, adult boosters, and vaccination in pregnancy (ViP). Nonetheless, pertussis remains a global health challenge with periodic outbreaks occurring every 2-5 years. The non-pharmacological measures implemented during the COVID-19 pandemic resulted in a drastic reduction in the circulation of B. pertussis. However, post-pandemic, there has been a resurgence in pertussis cases. This review aims to explore the post-pandemic global pertussis outbreaks and identify underlying trends to gain insights into the potential contributing factors. As of June 2025, pertussis outbreaks with diverse epidemiological patterns have been reported in at least 42 countries, including 30 aP and 12 wP vaccine-using countries. Some common observations among these countries include low infant immunization rates and an absence of vaccination programs for specific populations such as school-aged children, adults, and pregnant individuals. Additionally, in countries with extensive immunization schedules and high vaccination uptake, outbreaks have occurred in regions with low vaccination coverage rates (VCRs). Multiple interrelated factors may have contributed to the post-pandemic pertussis outbreaks, such as the cyclic epidemiology of pertussis, low VCR, waning vaccine-derived immunity, low uptake of boosters, and lack of lifelong protection through regular boosters. To effectively mitigate the incidence of pertussis outbreaks, it is crucial to administer regular booster vaccinations throughout an individual's lifetime, with particular emphasis on at-risk populations and pregnant individuals. A Graphical Abstract is available for this article.