Risk Factors for Hand, Foot and Mouth Disease Reinfection in Qingdao, China, from 2014 to 2022

Hand, foot and mouth disease (HFMD) is a common infection disease among children, which is caused by human enterovirus (EV) family. The absence of cross-protection against different EV sub-types, makes HFMD reinfection common. Thus, we aimed to explore the epidemiological characteristics and influencing factors of HFMD reinfection in Qingdao City.

Data on HFMD cases from 2014 to 2022 were obtained from National Infectious Surveillance System. Logistic regression analysis was used to assess the independent risk factors of HFMD reinfection.

Overall, 78422 HFMD cases were enrolled. Of these, 2041 cases were classified as reinfection, corresponding to the reinfection rate of 2.60%. The median time interval between the primary infection and secondary infection was 12.75 (IQR=12.24) months. The seasonal peak of reinfection occurred from June to August each year. Multivarite logistic analysis showed that male, younger age, scattered children, severe cases, hospitalization, and EV71 infection were risk factors for HFMD reinfection. The proportion of patients infected with EV71 in the primary infection cases was higher than that in non-reinfection cases (OR=1.83, 95%CI=1.29-2.60).

Boys aged 5 years and below, especially those with severe cases and first infected with EV71 are more prone to reinfection. Therefore, authorities should implement targeted health education and intervention strategies to reduce the reinfection rate among vulnerable population.