[Rubella immunity in Japanese women of childbearing age, 2008-2013: commercial diagnostic laboratory data analysis].

Background: For effective non-routine vaccination in women of childbearing age as a countermeasure against congenital rubella syndrome (CRS), it is important to know the specific age group in which fewer members have rubella immunity.
Methods: We analyzed rubella hemagglutination-inhibition (HI) antibody data (about 890,000) accumulated from 2008 through 2013 at a commercial diagnostic laboratory, which originated from the serum specimens sent mainly from obstetrics & gynecology clinics and hospital departments in Japan. Changes during the above period in the pattern of the annual curve for the prevalence of rubella antibodies (HI antibody titer > or = 8) by age, were observed.
Results: The antibody prevalence among women in their twenties decreased gradually from 2008 to 2013. However, the prevalence at < or = 22 years of age in the 2013 specimens was found to have risen, which we believe is the effect of the five-year interim vaccination program for high-school students that began in 2008. The lowest antibody prevalence at 23 years of age in 2013 corresponded to the highest numbers of female patients at the same age in the 2013 rubella epidemic among the adult population.
Conclusions: The analysis of extensive data accumulated for rubella antibodies assayed at the commercial diagnostic laboratory was useful for monitoring the susceptibility of the women to rubella infection in Japan, and that the Oct. 1987 to Mar. 1990 birth cohort (age 23 - 25 in 2013) is a high-risk group for CRS.