Evaluation of Mumps-specific Neutralizing Antibody Compared to Immunoglobulin G Antibody in Japanese Children After the Coronavirus Disease Pandemic.

Mumps vaccination, which is routinely administered in many countries, is not covered by Japan's national immunization program. Therefore, mumps epidemic occurs every 3 or 4 years in Japan due to a low vaccine coverage rate. To prepare for the next resurgence, we examined the immunity against mumps using neutralizing antibodies (NT) against vaccine strain (genotype B) and wildtype virus (genotype G), and mumps-specific enzyme immunoassay for immunoglobulin G (IgG). We enrolled 83 children admitted to the Kawasaki Medical Hospital for diseases other than mumps between April and December 2022. The positive rates of NT for both of wild type and vaccine type were lower (25 .3%) than that of IgG (38.5%). No significant difference among them. Though individual infection histories were not confirmed, the absence of any mumps epidemic during the coronavirus disease pandemic, Therefore, almost all enrolled children were unlikely to have been infected with mumps, that is, they might have acquired immunity only by voluntary vaccinations. Therefore, we evaluate the immunity for mumps in the real world at three novel points as follows, (1) to evaluate under non-national immunization program (2) to evaluate Hoshino vaccine strains (3) to evaluate both IgG and the other immunity.