Seroepidemiology of rubella infection in Chinese and Caucasians in Hong Kong

Abstract

The seroepidemiology of rubella infection in Hong Kong Chinese was examined by haemagglutination inhibition of normal sera and a comparison made where feasible with Caucasians living in Hong Kong. Taking reciprocal titre of 20 as a baseline, the incidence of maternally acquired antibody was 84% for Chinese and 90% for Caucasians. In babies up to 2 months this incidence was maintained in Caucasians but declined to 54% in Chinese. High titre antibody was more frequently detected in Caucasians generally, including women of child-bearing age. The detection of rubella-specific IgM in the Caucasian babies was suggestive of recent maternal infection. However, fewer Caucasian (20%) than Chinese (36%) women of child-bearing age (15–40 years) appeared unprotected against rubella. When all age groups were considered, 88% of Caucasians and 53% of Chinese were seropositive. The occurrence of a rubella outbreak during the study did not give rise to a significant increase in the incidence of seropositivity in Chinese 19–25 years, the only age group able to be evaluated in this manner. The ethnic differences in seroepidemiology are considered in the light of known HLA-1 and HLA-8 antigen distributions in Caucasian and Mongoloid people and the apparently low incidence of congenitally acquired rubella in Chinese.