To analyze the epidemiological characteristics, influential factors, and the risk of reinfection in patients with hand, foot and mouth disease (HFMD) in Xining, Qinghai, 2008-2023, and to provide scientific evidence for preventing HFMD reinfection in Xining and Qinghai-Tibet plateau regions.

The incidence data of HFMD in Xining from May 1, 2008 to December 31, 2023 were collected from the China Information System for Disease Control and Prevention to establish a database of cases of HFMD reinfection by filtering and organizing. Descriptive epidemiological method was used to describe the epidemiological characteristics of the reinfection cases, and the Kaplan-Meier method was utilized to assess the cumulative hazard probability of HFMD reinfection after initial infection, and Cox proportional hazards regression model was employed to conduct a comprehensive analysis of the risk of HFMD reinfection through both univariate and multivariate perspectives.

A total of 493 HFMD reinfection cases were reported in Xining 2008-2023, the reinfection incidence was 2.67% (493/18 472), and the cumulative risk for the reinfection was 3.00%. 486(98.58%) cases were infected twice, and 7 cases (1.42%) were infected three times. The Kaplan-Meier curve demonstrated that the cumulative risk of reinfection increased sharply within 30 months after the first infection, and with 74.44% of cases reinfected within 30 months. The Cox proportional hazards regression model analysis revealed that the risk of HFMD reinfection was lower in males compared to females (HR=0.822, 95% CI: 0.684-0.988), in children aged ≥3 years compared to those aged <3 years(HR=0.586, 95% CI: 0.445-0.771). The risk of HFMD reinfection was higher in kindergarten children (HR=5.551, 95% CI: 2.278-13.525) and scattered children (HR=6.897, 95% CI: 2.769-17.184) compared to other population groups, and in children residing in urban areas (HR=1.531, 95% CI: 1.222-1.917) compared to those in rural areas.

The reinfection rate of HFMD is relatively high in Xining. People living in urban areas, initially infected with enterovirus 71(EV71), boys under the age of 3, and scattered children have higher risk of HFMD reinfection. Targeted intervention measures ought to be implemented for these high-risk groups in order to effectively mitigate the reinfection incidence of HFMD.