[Epidemiological characteristics and immune effects of pertussis in Jiangxi Province, 2020-2023]

Objective: To analyze the epidemiological characteristics and immune effects of pertussis in Jiangxi Province from 2020 to 2023 and provide a reference basis for preventing and controlling pertussis in Jiangxi Province. Methods: The annual pertussis incidence data and population data of Jiangxi Province in the same period were derived from the China Disease Prevention and Control Information System, the population data for 2020 were derived from the seventh population census data of Jiangxi Province, and pertussis cases with PV immunization history were derived from the immunization program information system of Jiangxi Province. Descriptive epidemiological methods were used to analyze pertussis epidemic characteristics and PV immunization history in Jiangxi Province from 2020 to 2023. An expert modeler was used to construct the best time series model and perform seasonal decomposition. The chi-square test and Cochran-Armitage trend test were used for statistical analysis. Excel 2013 and SPSS 27.0 software were used for statistical analysis. Results: A total of 886 cases of pertussis were reported in Jiangxi Province from 2020 to 2023, with an average annual reported incidence rate of 0.49/100 000, showing a linear upward trend (Z=121.80, P<0.001). The Winters' additive model was optimal to fit the monthly data with stable seasonality (Ljung-Box statistic Q=10.56, P=0.78), the average number of reported cases in August was higher than the annual average of 5.12. The top three cities with reported incidence rates were Pingxiang (1.11/100 000), Yichun (1.10/100 000), and Nanchang (0.73/100 000). The highest age composition of cases was in the under 1-year-old group (373 cases,42.10%). Under 1-year-old group, 5-9-years-old group, and ≥10-years-old group all showed an increasing trend in reported incidence year by year (all P<0.001), and the reported incidence rate of under 1-year-old group increased from 12.42/100 000 in 2020 to 48.85/100 000 in 2023. A total of 545 cases (61.51%) had a history of PV immunization. Four doses PV immunization was the main ones (44.92%, 398 cases) and the median (Q₁, Q₃) interval from the last vaccination to onset was 4 (1,5) years. Conclusions: The reported incidence of pertussis in Jiangxi Province increased from 2020 to 2023. The cases are mainly concentrated in the under 1-year-old group. The rates of PV vaccination in pertussis cases was low, with more number of vaccine breakthrough infection cases with 4-doses PV vaccination. It has been suggested to continue doing the following: strengthening pertussis surveillance, improving the timeliness of pertussis vaccination, implementing the fifth dose as soon as possible for children over 6-year-old, strengthening the studies of vaccine breakthrough infection case, and optimizing the population immunity strategy of pertussis.