Persistence of anti-rubella immunoglobulin G antibody titers in young adults involved in a short-term periodic immunization in Japan.

In Japan, several rubella outbreaks in adults have erupted due to insufficient immunity against rubella virus (RUBV). Although selective immunization is being promoted in addition to a routine rubella vaccine program as a rubella eradication strategy, serosurveillance against RUBV needs to be implemented in the generations corresponding to the transition period of vaccination. In this study, a survey of anti-rubella immunoglobulin G (IgG) antibody titers was conducted among young adults involved in the transitional periods of the routine rubella vaccine program. Serosurveillance was performed in 370 healthy young adults aged 18-20 years, and their serum samples were analyzed using an enzyme immunoassay to determine rubella-specific IgG antibody titers. Although multiple regression analysis revealed significant differences only in medical history, more than 90% of participants exhibited seropositivity, excluding those who received single-dose vaccine alone. Based on elapsed periods after the last vaccination, rubella-specific IgG antibody titers in less than a 6-year period were higher compared to that in the more than 10-year period. Although almost all study participants in the transitional period had seropositivity, the results may indicate that the persistence of seropositivity is related to past rubella outbreaks.