Immunogenicity and efficacy of one dose measles-mumps-rubella (MMR) vaccine at twelve months of age as compared to monovalent measles vaccination at nine months followed by MMR revaccination at fifteen months of age

Background and methods: measles is a common cause of morbidity and mortalit y in developing countries. Although the measles -mumps - rubella vaccine (M MR) is currently in use in developed countries, monovalent measles vaccine (MV) is routinely recommended by World Health Organization (WHO) at 9 month s of age in Turkey. as in many other developing countries. In this study, 4 42 Turkish children received MV at 9 months of age and were revaccinated wi th MMR vaccine at 15 months of age. In the second group 495 children receiv ed MMR at 12 months of age with no earlier measles vaccination. Antibodies were measured before the first vaccination and 6 weeks after the MMR, All c hildren had been followed for occurrence of measles infection for 60 months . Two vaccination schedules were compared for immunogenicity and protection rates. Conclusions: seroconversion and clinical protection rates were sign ificantly higher in children who received only MMR at 12 months of age than in children revaccinated at 15 months of age. Seroconversion rate for meas les was 69.9% in children who received MMR at 12 months of age and 90.3% in children revaccinated at 15 months of age (P = 0.0003). While there was no measles case in children who were revaccinated. 12 (2.7%) children in the first group acquired measles during the follow-up period. Vaccination at 12 months of age appeared to be better than the current national standard. Th e late elimination of maternal antibodies and the inhibitory effect of a we ak antibody response after the first dose of vaccine at 9 months may explai n the better immunogenicity and efficacy of the MMR vaccine given at 12 mon ths of age. (C) 2001 Published by Elsevier Science Ltd.