Objectives A 5-step study was conducted to investigate the immunogenicity of the Hoshino strain of mumps (included in MMR vaccine).

Methods A total of 338 schoolchildren subjects were selected. Blood samples were collected, and sera tested by ELISA for detection of mumps IgG and IgM.

Results Overall, 19.8% (67 persons) of subjects did not have antibodies to mumps virus. These persons have been invited for MMR vaccination, but 44 of them accepted to be vaccinated and 40 persons continued till the end of the study. Due to seroconversion of four persons (new infection) they have been excluded and finally 36 persons remained in last three steps of the study. There were two groups of persons, 6–11 years old (20 persons) and 12–14 years old (16 persons). All samples tested by ELISA for detection of mumps IgM and IgG as: (IgM1 and IgG1 for the time of vaccination), (IgM2 and IgG2 for 3 months later), (IgM3 and IgG3 for 12th month) and (IgG4 for 24th month). The seroconversion rate was reported as 86.1%, 77.7% and 75% for total at the third, 12th and 24th months following vaccination.

Conclusion With one dose vaccination of Hoshino strain of mumps, there is a decline of antibody levels to 75% after 2 years, which is similar to natural infection. So it may be logistic to recommend strongly for booster dose of vaccination after using this strain in children.

Keywords: immunity; mumps; vaccination