Suppression of Measles 19S Antibody Formation as Evidence of Immunity

Secondary immune responses to measles virus are characterized by a rise in 7S measles antibodies with little or no 19S antibody production. Sera collected a month after challenge with live measles vaccine of 9-month-old infants who had received inactivated measles vaccine before they were 7 months of age revealed 19S antibodies in 50% of postchallenge sera tested. Suppression of 19S antibody formation in the other 50% was well correlated with resistance to the clinical effects of measles and provided a more sensitive measure of immunization during the maternal antibody period than seroconversion or incidence of clinical reactions to challenge.