Age of measles immunization in tropics.

Maternal immunity to measles was studied in a group of 500 newborn children and another group of 500 children aged one to 12 months, before vaccination. The geometric mean titer of detectable hemagglutination-inhibition antibody was 16 for newborn children. This titer was absent in most children aged 3 to 5 months. Our previous studies indicate that from 1970 to 1972, children from the lower socio-economic classes aged 5 to 9 months were the main target of measles complications and deaths. Based on the present data, we suggest that children in developing countries should be vaccinated as young as 6 months and should be revaccinated 3 to 4 months later to assure full protection.