Immunogenicity of measles-rubella vaccine administered under India's Universal Immunization Programme in the context of measles-rubella elimination goal: A longitudinal study.

Background & Objectives: There is a paucity of data regarding immunogenicity of recently introduced measles-rubella (MR) vaccine in Indian children, in which the first dose is administered below one year of age. This study was undertaken to assess the immunogenicity against rubella and measles 4-6 wk after one and two doses of MR vaccine administered under India's Universal Immunization Programme (UIP).

Methods: In this longitudinal study, 100 consecutive healthy infants (9-12 months) of either gender attending the immunization clinic of a tertiary care government hospital affiliated to a medical college of Delhi for the first dose of routine MR vaccination were enrolled. MR vaccine (0.5 ml, subcutaneous) was administered to the enrolled participants (1 dose at 9-12 months and 2 dose at 15-24 months). On each follow up (4-6 wk post-vaccination), 2 ml of venous blood sample was collected to estimate the antibody titres against measles and rubella using quantitative ELISA kits. Seroprotection (>10 IU/ml for measles and >10 WHO U/ml for rubella) and antibody titres were evaluated after each dose.

Results: The seroprotection rate against rubella was 97.5 and 100 per cent and against measles was 88.7 per cent and 100 per cent 4-6 wk after the first and second doses, respectively. The mean (standard deviation) titres against rubella and measles increased significantly (P<0.001) after the second dose in comparison to the levels after the first dose by about 100 per cent and 20 per cent, respectively.

Interpretation & Conclusions: MR vaccine administered below one year of age under the UIP resulted in seroprotection against rubella and measles in a large majority of children. Furthermore, its second dose resulted in seroprotection of all children. The current MR vaccination strategy of two doses, out of which the first is to be given to infants below one year of age, appears robust and justifiable among Indian children.