Optimal age for vaccinating Nigerian children against measles. I. Neonatal antibody profile and subsequent susceptibility to measles.

The decline of maternally acquired haemagglutination inhibiting antibodies against measles virus in Nigerian children born in Lagos was studied. At birth all the 303 children whose cord blood serum was tested had measurable antibodies. The antibody titre remained detectable in all the children up to four months of age, and in over 90% at five months of age. At six months 65% of the children were without detectable antibodies. At seven and eight months the proportion of children without measurable antibodies was reduced to 50% and 42% respectively, indicating a slight but progressive improvement in the immune status of the children. These findings provide a serological basis for starting anti-measles immunization of Nigerian children at six months.