ABSTRACT
A field evaluation of measles vaccine efficacy was undertaken in resettlement colonies in New Seemapuri, Shahdara Zone, Delhi, having an estimated population of 20,500 by case-reference method. The standard 30 cluster sampling technique was adopted and 261 measles vaccinated children were matched with 545 measles non-vaccinated children. The attack rate of measles was found to be 4.2 and 30.3 per cent in measles vaccinated and non-vaccinated children respectively, which is statistically highly significant (P less than 0.001). The relative risk of developing measles in non-vaccinated child is seven times more as compared to a vaccinated child. Vaccine efficacy (V.E.) evaluated by different epidemiological and laboratory methods was found to be 86.1 per cent +/- 11 at P = 0.05. Further, a large scale study on measles V.E. is recommended in different parts of the country by case-reference method, as it is found to be simple, reproducible and easy to undertake in a field situation.