Epidemiological characteristics of hepatitis A in Yuxi city, 1994–2023

Objective: To analyze the epidemiological characteristics of hepatitis A virus infection in Yuxi City from 1994 to 2023, and examine changes in its incidence rate before (1994-2008) and after (2009-2023) the inclusion of the attenuated hepatitis A vaccine in the Expanded Program on Immunization (EPI). Methods: Data on reported hepatitis A cases in Yuxi City, Yunnan Province from 1994 to 2023 were collected from the Yuxi City Epidemic Data Compilation and the China Disease Prevention and Control Information System. The analysis examined changes in hepatitis A incidence rates before and after the inclusion of the hepatitis A vaccine in the EPI in 2008. Seasonality in hepatitis A incidence was analyzed using the concentration method. Results: From 1994 to 2023, Yuxi City reported a total of 6 028 cases of hepatitis A, with an average annual incidence rate of 9.75/100 000. The reported incidence rate showed an overall downward trend over the years (χ²_trend = 3 566.82, P<0.001). The annual incidence rate decreased from 16.78/100 000 before the EPI (1994-2008) to 2.72 /100 000 after EPI implementation (2009-2023). No seasonal variation was observed in incidence before or after EPI (1994-2023: M=0.184; pre-EPI: M=0.207; post-EPI: M=0.059). Regarding occupational distribution, pre-EPI cases predominantly involved students (37.20%), while post-EPI cases primarily involved farmers (48.73%). The reported incidence rate of hepatitis A was higher among males (11.47/100 000) than females (7.98/100 000). Cases occurred across all age groups, with the annual average reported incidence rate decreasing with increasing age. Post-EPI, the highest reported incidence rate was observed in the 30-39 age group (0.72/100 000). From 1994 to 2023, the top three counties (cities, districts) in cumulative reported incidence in Yuxi City were Tonghai County (18.41/100 000), Eshan County (15.42/100 000), and Jiangchuan District (10.34/100 000). Following the implementation of the EPI, reported incidence rates of hepatitis A declined significantly across all regions, with the average incidence rate decreasing from 17.50/100 000 to 2.31/100 000. When categorizing Yuxi City's nine counties (cities and districts) into three groups based on their gross domestic product (GDP) levels, the reported incidence of hepatitis A decreased as regional GDP levels increased. Conclusion: Following the inclusion of hepatitis A vaccines in Yuxi City's EPI, the incidence of hepatitis A has declined. Farmers and individuals aged 30-<45 constitute key target groups for hepatitis A prevention and control, while regions with lower GDP levels represent priority areas for intervention. Efforts should focus on expanding vaccination coverage among these priority populations in key regions, while simultaneously strengthening health education and environmental improvements to consolidate prevention outcomes and reduce disparities in disease incidence.