SEROLOGIC RESPONSES TO MEASLES, MUMPS, AND RUBELLA (MMR) VACCINE IN HEALTHY INFANTS - FAILURE TO RESPOND TO MEASLES AND MUMPS COMPONENTS MAY INFLUENCE DECISIONS ON TIMING OF THE 2ND DOSE OF MMR

Measles, mumps, and rubella-specific IgG antibodies were evaluated in 134 healthy infants routinely immunized with trivalent live attenuated measles-mumps-rubella (MMR) vaccine at one year of age. Blood samples were collected just before, and at 1, 3, and 12 months after MMR. Spe cific IgG was measured by commercial enzyme immunoassays. Before vacci nation, 98.5%, 99.2%, and 98.5% of the infants tested were seronegativ e for measles, mumps, and rubella, respectively. One year after MMR, 1 6.4% and 22.4% of vaccinees lacked demonstrable antibody to measles an d mumps while none were found to be seronegative for rubella. Response profile analysis revealed primary failure rates of 12.1% (measles) an d 8.6% (mumps) while 4% (measles) and 13.8% (mumps) of the infants res ponded initially but became seronegative within one year. These observ ations suggest that earlier administration (at age 18 months) of the s econd dose of MMR may be more desirable than revaccination at school e ntry.