[Rubella immunity in Japanese women 20- 39-years-old, 1999-2007: commercial diagnostic laboratory data analysis]

We analyzed rubella antibody data from hemagglutination-inhibition tests on 600,000 serum specimens from Japanese women 20- 39-years-old. Specimens had been sent by gynecology clinics nationwide to a commercial diagnostic laboratory from 1999 through 2007. Antibody-positive percentages in women in their 20s to mid 30s in 1999 to 2001 were 95%, while those in women in their early 20s from 2002 to 2007 were lower at 88% among 20-year-olds in 2002 born in 1982 and 86% among those in 2007 born in 1987. These lower percentages resulted from a change in rubella vaccination policy under which junior high school girls between 1977 and 1994-those born between 1962 and 1981-underwent mandatory rubella vaccination, while mandatory vaccination was administered to younger children, instead, from 1995. Due to this policy change, girls born between 1982 and 1987 were not subjected to mandatory vaccination. We believe that women in this group have a relatively higher risk of bearing children with congenital rubella syndrome (CRS). Additional campaigns for voluntary rubella vaccination should thus be addressed to this female cohort.