Rubella-neutralizing and haemagglutinin-inhibiting antibodies in children of different ages.

Rubella neutralization and haemagglutinin-inhibition tests were used to determine the incidence of rubella antibodies in the sera of 235 children and adolescents aged 1 month to 20 years. The tests showed good agreement in the detection of rubella antibodies resulting from acute infection. Maternal antibodies became undetectable within six months after birth. The proportion of children possessing rubella antibodies was found to be about 23% by the age of 5 years, rising sharply to 80% in the 6-12 years age group and 83% in the 13-20 years age group. Results indicate that the incidence of rubella infection may be higher in females than in males. The correlation between statements concerning a past history of rubella and immune status was poor, particularly in the older age groups. Any policy for vaccination against rubella must take into account the difficulties of identifying nonimmune persons in a large population.