Seroprevalence of Neutralizing Antibodies against Candidate Serotypes of Enterovirus Vaccines among Korean Children

Hand, foot, and mouth disease (HFMD) is a pediatric public health concern in Asia. Surveillance data on the circulating serotypes of HFMD suggest that Enterovirus A71 (EV-A71) and coxsackieviruses A6, A10, and A16 (CVA6, CVA10, and CVA16) are the major serotypes causing HFMD. Asian countries, including Korea, are currently developing a multivalent vaccine targeting these serotypes. However, the immunity of children against specific serotypes, indicating past infection, should also be considered while selecting candidate serotypes for vaccine development. Therefore, we aimed to identify the age-stratified serological statuses of Korean children to determine candidate serotypes for HFMD vaccine development. This study included 220 participants, categorized into four age groups, 7 months-2 years, 3-5 years, 6-10 years, and 11-15 years. A neutralization test was performed to quantitate the neutralizing antibodies (NtAbs) in the sera of the participants. Only EV-A71 and CVA6 were found suitable as candidate serotypes for vaccine development, whereas further study is needed for CVA10 and CVA16. The highest seropositivity and NtAb titer ranges were observed for CVA6 in all age groups, suggesting that the participants had been predominantly exposed to CVA6. For EV-A71, seropositivity and NtAb titer ranges steadily increased with age, suggesting that children were currently exposed to EV-A71. For CVA10, the 3-5 years group showed the highest seropositivity rate and higher NtAb titer ranges than the older age groups, indicating that the exposure to CVA10 had mainly occurred in recent years. Future studies will identify whether the exposure to CVA10 was transient or will continue. For CVA16, seropositivity and NtAb titer ranges were generally low, indicating that only a few participants had been exposed to CVA16. We identified discrepancies between the sentinel surveillance data and our findings. This study provides a new perspective for HFMD vaccine development and policy making in Asian countries.