How to prevent rubella epidemics and congenital rubella syndrome: lessons from 42 years of longitudinal epidemiology in Osaka Prefecture, Japan (1982-2023).

BACKGROUND: Despite the introduction of rubella-containing vaccine into routine immunization in 1977, rubella has not been eliminated in Japan. This study aimed to validate the immunization strategy and to highlight the crucial elements of elimination program. METHODS: We scrutinized cases of rubella and congenital rubella syndrome (CRS). Additionally, we analyzed the national vaccination coverage, seroprevalence, and number of maternal rubella-related spontaneous or artificial fetal deaths. RESULTS: The shift from selective to universal immunization significantly reduced rubella cases coupled with increased seroprevalence in children. However, rubella resurged in 2012-2013 and 2018-2019, which was virologically and serologically confirmed to be associated with imported rubella virus (RuV) and susceptible males. Although the disease burden of CRS may have been suppressed in the past by the large number of spontaneous or artificial fetal deaths, the incidence rate of CRS was comparable to that of the 1960s to 1980s. Cases of breakthrough infection and CRS were identified in females who were considered to have a history of single-dose vaccination. CONCLUSIONS: Even with universal immunization, future epidemics and severe outcomes cannot be prevented unless immunization gaps are closed. Furthermore, CRS and breakthrough infection are not completely prevented by single-dose vaccination, indicating the need for second-dose vaccination.

Comparison of virological and serological methods for laboratory confirmation of rubella.

BACKGROUND: Work toward rubella elimination has accelerated globally. A reliable laboratory confirmation of rubella-suspected cases is required for effective surveillance in the rubella-elimination phase. The use of adequate specimens is a key to improving the quality of this surveillance. STUDY DESIGN: We conducted rubella virus (RUBV) isolation and RUBV genome or anti-RUBV IgM detection on 1023 specimens from 372 rubella- or measles-suspected cases collected through the national surveillance program in Sakai city of Osaka prefecture, Japan between 2011 and 2013. The resulting data were analyzed by specimen type, collection date, and immunological status. RESULTS: Among the three specimen types (throat swab, serum or plasma, and urine) collected through 10 days post-rash onset, the highest success rates for RUBV genome detection and RUBV isolation were obtained using throat swabs. In agreement with previous work, RUBV-specific IgM were undetectable in 50% of the rubella-confirmed cases until 3 days after rash onset. The success rates of RUBV genome detection and RUBV isolation declined in association with the appearance of RUBV-specific antibodies in blood, especially in serum, plasma, or urine samples. CONCLUSION: Throat swabs are the most optimal specimen types for both RUBV genome detection and RUBV isolation; serum/plasma samples may be suboptimal, especially for RUBV isolation. The findings from this study will provide useful information for improving laboratory surveillance for rubella in the elimination phase.