[Trend analysis of rotavirus diarrhea incidence among children aged 5 years and under in Shanghai City from 2015 to 2023].

Objective: To analyze the temporal trend of reported incidence of rotavirus diarrhea among children aged 5 years and under in Shanghai from 2015 to 2023, and to identify the effects of age, period, and birth cohort. Methods: Confirmed cases of other infectious diarrhea, a legally notifiable Class C infectious disease, reported between July 1, 2015, and June 30, 2023, among residents of Shanghai were selected. Rotavirus-positive cases aged 5 years and under were further identified, and the reported incidence was calculated. A Bayesian age-period-cohort (BAPC) model was established to assess the independent effects of age, period, and birth cohort on the reported incidence of rotavirus diarrhea, with the year immediately preceding the introduction of the new rotavirus vaccine designated as the reference category for both period and cohort. Results: From 2015 to 2023, the annual reported incidence rate of rotavirus diarrhea among children aged 5 years and under in Shanghai was 89.5/100 000, with rates consistently above 136/100 000 between 2015 and 2018, and below 62/100 000 from 2019 to 2023. The incidence rate in children aged 0 year (140.5/100 000) and 1 year (211.6/100 000) was higher, while the incidence rate in children aged 4-5 years (25.1/100 000) was lower. In the BAPC model, the age effect revealed a decline in incidence risk beyond 1 year. The period effect indicated a significant reduction in incidence risk after 2017-2018 (RR=0.34, 0.67, 0.36). The cohort effect demonstrated that the incidence rate among those born from 2018 to 2021 was significantly lower than that of those born in 2017 (RR=0.80, 0.70, 0.56, 0.48). Conclusion: The reported incidence of rotavirus diarrhea is higher among children under 2 years. The risk of rotavirus diarrhea is significantly lower in birth cohorts from 2018 to 2021 than that in the 2017 to 2018 birth cohort.