Study on the resurgence of pertussis based on a stage-structured dynamic model

Although pertussis vaccination has effectively reduced the global incidence rate and mortality, pertussis resurgence has been observed in many countries in recent years. This study aims to untangle the changes in dynamic transmission characteristics before and after pertussis resurgence in high-incidence provinces of China and to explore the contributing factors and potential control measures. Shandong, Sichuan, and Zhejiang provinces were selected as study subjects. Based on monthly cases data from 2004 to 2022, dynamic models incorporating different waning immunity were constructed to identify the model that most appropriately reflected the epidemic dynamics in these provinces. From 2004 to 2013 in Shandong Province, and from 2004 to 2017 in Zhejiang and Sichuan Province, the Susceptible-Vaccinated-Infected-Recovered model (SVIR) best captured the epidemic dynamics in the three provinces, with an estimated vaccine protection duration of approximately 7-11 years. After the resurgence, the Susceptible-Vaccinated-Infected-Recovered-Susceptible model (SVIRS) more accurately represented the epidemic dynamics across the three provinces, with vaccine protection lasting 7-13 years and natural immunity persisting for 16-24 years, indicating the absence of lifelong immunity. Moreover, we found increases in the average transmission rate, case reporting, and vaccine effectiveness for pertussis. The observed resurgence of pertussis in the three provinces in China is affected by multiple factors, including elevated transmission rates, improved reporting rate, and vaccine-induced immunity waning. To mitigate resurgence, booster vaccination strategies targeting adolescents and adults should be considered.