Comparative evaluation of measles, mumps & rubella vaccine at 9 & 15 months of age.

Background & Objectives: Measles, mumps and rubella (MMR) contribute to significant amount of mortality and morbidity in our country. Though MMR vaccine has been a part of immunization schedule in the developed countries, it is yet to be included in our national immunization schedule. Hence this study was conducted to assess the serological status of measles, mumps and rubella in young children and to evaluate the seroconversion of measles, mumps and rubella vaccine at 9 and 15 months of age.

Methods: The cohort study was carried out at the out patient department of a tertiary care hospital in north India. A total of 240 normal children, 120 each in the age group 9-10 and 15-18 months attending the hospital for immunization were enrolled for the study. None of them had been vaccinated with MMR vaccine in the past, or gave any history of measles, mumps or rubella infection, or were on any immunosuppressive agent. The pre-vaccination blood sample was taken and each child was administered a single dose of trivalent MMR vaccine. The post-vaccination sample was taken 6-8 wk later. The paired serum samples were analysed for the presence of measles, mumps and rubella antibodies using commercially available ELISA kits.

Results: Of the 120 infants in the age group of 9-10 months, 102 (85%) were seronegative for measles and 96 (80%) were seronegative for both mumps and rubella. Following MMR vaccination, 102 infants came for post vaccination sampling of which 92 per cent were seropositive for measles, 100 per cent for mumps and 98 per cent for rubella. In the age group of 15-18 months, of the 120 children, 67 (56%) were seronegative for measles, 84 (70%) for mumps and 86 (71.6%) for rubella. In 50 per cent of the children, there was a history of measles immunization at 9 months of age. After MMR vaccination, 100 children came for post vaccination sampling and seropositivity of 92, 96 and 94 per cent was observed for measles, mumps and rubella, respectively. The rise in the pre- and post-immunization geometrical mean titre was significant (P < 0.05) for each component of the vaccine in both the age groups.

Interpretation & Conclusion: The MMR vaccine can be offered safely and with equal efficacy to children at 9 and 15 months of age.