Evidence for reinstatement of infants 12 to 14 months of age into routine measles immunization programs.

The hemagglutination inhibition (HI) serologic responses of 851 measles-susceptible infants and children to the live, further-attenuated measles virus vaccine were evaluated over a ten-year period. The response by age at 23-day intervals was determined. Infants inoculated at 12 through 14 months of age demonstrated seroconversion rates by HI assay comparable to those in infants and children inoculated at 15 months of age or older. This finding does not support the recent recommendation that routine active immunization with measles vaccine should be postponed until 15 months of age. We emphasize the possible consequence of electively leaving infants 12 throught 14 months of age vulnerable to measles because of the current endemicity of this disease in the United States. We also present evidence for the reinstatement of infants 12 through 14 months of age into routine measles immunization programs and for the need to further evaluate the causes for vaccine failure in vaccines after the loss of maternal antibody.