Public health implications of rubella antibody levels in California

Rubella hemaggluttination inhibition (HI) antibody determination were performed in 1977 on a sample of California school children and in 1977-1979 on young women who were about to be married or who were pregnant. Among the pupils, 66 per cent reported prior rubella immunization; immunization history was more common in younger pupils. Seventy-seven per cent had detectable antibody, with little trend of greater seropositivity at older ages. Over 86 per cent of those with a written record of immunization had detectable antibody. There was no consistent indication of loss of seropositivity with increasing time since immunization. Children immunized at 12-14 months of age tended to have a lower seropositivity rate than those immunized at older ages. Among young women, the prevalence of detectable antibody was 80-83 per cent. Comparison with data obtained in 1968-1969 indicates that rubella immunization has had a marked impact on levels in teenagers and adults. The pool of rubella-susceptibles entering secondary schools will probably not decrease soon, so that rubella outbreaks may continue in high school and college-age populations. Ultimately, school entry immunization requirements should drastically curtail disease activity. In the interim, programs to immunize teenagers and young adult females must be strengthened.