COMPARISON OF PROTECTION AFFORDED BY SINGLE MEASLES VACCINATION AND LATE REVACCINATION SCHEDULES

An intervention study compared the protection afforded vaccinees by si ngle measles vaccination and late revaccination schedules in 1990-94, During the intervention a single revaccination (after initial vaccinat ion at nine months of age) was applied to children at any point in tim e between 12 and 23 months of age. Cases of measles aged 10-23 months were identified through an active surveillance system and in this peri od 5, 11 and 11 cases of revaccinated, single vaccination and unvaccin ated children were identified. Measles incidence rates were 392.2-415. 6 (mean=405.6, SD=6.7), 75.4-112.1 (median=91.7, SD=13.3) and 12.8-15. 2 (mean=13.9, SD=0.99) per 100 000 population in children who were unv accinated, with single vaccination and revaccinated respectively. Rela tive risk of contracting measles in children who were unvaccinated or with single vaccination was 26.5-32.5 (mean=29.4, SD=2.3) and 5.8-8.8 (mean=6.8, SD=1.2) respectively compared with revaccinated children, V accine efficacies that were determined were 73-81% (mean=77.2, SD=2.9) and 96.2-96.9% (mean=96.6, SD=0.27) for single vaccination and late r evaccination schedules respectively. It was concluded that late revacc ination affords vaccinees better protection than single vaccination th rough improvement in vaccine.