Objective: To measure the protective effect of measles vaccine administered before 9 months of age and compare overall mortality of children vaccinated at 6-8 months and at 9-11 months.
Method: Non-concurrent cohort study involving all 13 134 children born between 16 January 1986 and 31st December 1991 in Kaniyambadi block near Vellore who had not left the area by six months of age. Main outcome measures were risk of disease and death among the under-five-year-olds according to age at measles immunization.
Results: Unimmunized children had a higher risk of developing measles compared to the immunized (P < 0.05). There was no significant difference in risk of measles among those vaccinated prior to and after nine months of age. Unvaccinated children were at significantly higher risk of death than vaccinated children (P < 0.001). There was no difference in risk of death between infants vaccinated between 6 and 8 months and those vaccinated between 9 and 11 months. There was no difference in the risk of death between boys and girls vaccinated between 6 and 8 months with standard-titre Edmonston-Zagreb vaccine.
Conclusion: Administration of standard-titre Edmonston-Zagreb measles vaccine at 6-8 months is an effective and safe preventive measure for measles, especially where the age-specific attack rate for children < 9 months is high.