Background. Maternally derived passive measles antibody may interfere with vaccine-
induced immunity in infants less than 12 months of age. However, early loss of passive
measles antibody may occur in infants of women who received measles vaccine because
measles vaccine induces lower antibody titers than does natural infection. Methods.
Persistence of passive neutralizing measles antibody was studied longitudinally in a group
of normal infants as a function of maternal measles titer at birth and maternal date of birth …