[Evaluation of the impact of the Japanese encephalitis vaccine included in an expanded immunization program on the reported incidence rate of Japanese encephalitis in Gansu province-based on interrupted time series]

Objective: To evaluate the impact of the Japanese encephalitis vaccine included in an expanded immunization program on the reported incidence rate of Japanese encephalitis in Gansu province. Methods: Information on the reported incidence rate of Japanese encephalitis in Gansu province from 1987 to 2019 was collected through the National Population Health Science Data Center and the China Disease Prevention and Control Information System. In addition, the trend of Japanese encephalitis reported incidence rate in Gansu province before and after the inclusion of the Japanese encephalitis vaccine in the expanded immunization program was analyzed using an interrupted time-series design. Results: The annual reported incidence rate of Japanese encephalitis in Gansu province from 1987 to 2019 was 0.448/per 100 000. However, after the inclusion of the Japanese encephalitis vaccine in the expanded immunization program in Gansu province in 2008, the amount of change in the level of Japanese encephalitis reported incidence rate was -2.223/per 100 000 (t=-2.90, P=0.007), the amount of change in the slope of Japanese encephalitis reported incidence rate was 0.082 (t=2.87, P=0.008) with the slope of Japanese encephalitis reported incidence rate as 0.071 (β₁+β₃=0.071). Conclusions: The Japanese encephalitis vaccine has achieved good prevention and control effects in Gansu province in the short term after its inclusion in the expanded immunization program, but outbreaks of Japanese encephalitis have still occurred. Therefore, in the future, Gansu province should promptly adjust the immunization strategy of the Japanese encephalitis vaccine, and strengthen the vaccination of the adult population, especially the rural adult population in the southeastern region of Gansu province, based on the continued focus on the works on Japanese encephalitis vaccination for children and adolescents.