Positive rates for rubella antibody in pregnant women and benefit of post‐partum vaccination in a Japanese perinatal center

Abstract

This study of pregnant women was undertaken to clarify their immune status for rubella and to evaluate the efficacy of, and adverse reaction to, post-partum rubella vaccination. We determined the levels of both rubella antibody by hemagglutination inhibition test and IgM antibody by enzyme-linked immunosorbent assay in the first gestational trimester and surveyed the positive rates for rubella antibody in pregnant women at our perinatal center; we recommended post-partum vaccination for women with poor immune status. We also evaluated the effectiveness of the vaccine and any adverse reaction. Among 2741 pregnant women, 185 cases (6.7%) were seronegative for rubella virus. This rate was especially high (12.4%) in the population who had opted out of the vaccination because of a change in Japanese government policy. A total of 30 cases (1.1%) were positive or false-positive for IgM antibody, but no congenital rubella syndrome (CRS) developed. The seropositive rate was 93.3% in total, but this figure includes those who required post-partum vaccination (558 cases or 20.3%) because their titers were 16x or lower. Among 145 cases who received post-partum rubella vaccine, no severe adverse reaction was detected, and in all 37 cases with hemagglutination inhibition antibody titers of 8x or lower, the efficacy rate was 100%. It is necessary to appropriately evaluate the CRS risk. Also, we need to emphasize the importance and safety of post-partum rubella vaccination in Japan.