Comparing catch-up vaccination programs based on analysis of 2012-13 rubella outbreak in Kawasaki City, Japan

Difficulty in Serologic Screening for Subclinical Rubella during Pregnancy

In Japan, rubella antibodies are tested in all pregnant women to detect subclinical infections. This study aimed to assess the validity of measuring rubella antibodies for detecting subclinical rubella among pregnant women in Japan. This single-center retrospective study measured rubella hemagglutination inhibition (HI) titers and rubella-specific IgM antibody index (IgM) values. IgM values were measured by conducting enzyme immunoassay, and IgM-values >1.2 were considered positive. Of 14,965 included pregnant women, 186 (1.2%) were IgM-positive. Only one patient was clinically diagnosed with rubella (HI titer, 1:2,048; IgM value, 10) and developed fever and skin rash. She decided to terminate her pregnancy without undergoing repeated blood tests. Of the IgM-positive patients, 136 (73.1%) had rubella HI titers of < 1:256. The correlation coefficient between rubella HI and IgM titers was weakly positive (0.2527; P < 0.0001). This study showed that a single combination of rubella HI and rubella-specific IgM measurements alone could not detect subclinical rubella. Creating awareness among pregnant women by informing them that almost all rubella-specific IgM-positive individuals without symptoms are not acutely infected could decrease their anxiety and prevent unnecessary pregnancy termination.

Factors Predicting Rubella Vaccination and Antibody in Pregnant Women in Japan: A Report from Pregnant Women Health Initiative

This study aimed to identify the factors predicting rubella vaccination status based on self-reported data and the presence of sufficient rubella antibody titers in pregnant women in Japan. We used the results of the nationwide questionnaire survey conducted at obstetric facilities in the Pregnant Women Health Initiative Project (PWHI), with 23 participating hospitals recruiting pregnant women from June 2018–November 2019. We extracted age, the number of deliveries, educational level, household income, pre-pregnancy smoking, and knowledge of rubella from questionnaires and medical records. We analyzed the association of rubella vaccination status and antibodies with each of these factors. We found that the number of previous deliveries, educational level, annual household income, smoking before pregnancy, and knowledge of rubella were factors predicting self-reported rubella vaccination status, while age and the number of previous deliveries were identified as factors predicting the presence of sufficient rubella antibody titers (32 folds or higher). Women considering pregnancy should be immunized against rubella to prevent congenital rubella syndrome in the future. Furthermore, social policies are needed to strongly encourage vaccination, especially for all citizens who were not given the opportunity or missed the chance to be vaccinated against rubella.