Rubella seronegativity in antenatal screening – Is it influenced by the introduction of universal childhood rubella immunization?

Abstract

ObjectiveThis study examined the impact of rubella immunization, implemented in Hong Kong in phases since 1978, on antenatal rubella serological status in Chinese women. MethodsIn a retrospective cohort study, the incidence of antenatal rubella seronegative status in our parturients managed from 1998 to 2013 was analyzed by their year-of-birth as follows: <1965 (no childhood immunization), 1965–1982 (single dose at Primary 6), and ≥1983 (two doses at age 12 months and 12 years), adjusting for other factors including age, parity, body mass index, place-of-birth status and hepatitis B surface antigen (HBsAg) status. FindingsRubella seronegativity decreased from 12.9%, 10.5%, to 9.8% respectively, and correlated inversely (P<0.001) with year-of-birth cohorts. Despite similar demographic profiles, this correlation was found only in Hong-Kong-born women (from 12.6%, 7.5% to 6.5% respectively), who also had significant lower incidences of rubella seronegativity (OR 0.73, 0.31 and 0.29 respectively) and HBsAg seropositivity (OR 1.09, 0.63 and 0.48 respectively) than China-born women. On regression analysis, rubella seronegativity was actually significantly increased following the implementation of immunization (aOR 1.20) while it was the reverse for non-residents (aOR 0.61). ConclusionAlthough rubella seronegativity decreased with immunization, the effect was less than expected when adjusted for other risk factors.