The optimal age for vaccination against measles in an Asiatic city, Taipei, Taiwan: reduction of vaccine induced titre by residual transplacental antibody.

Children vaccinated when aged between six and thirteen months against measles in Taipei showed a high frequency of response, similar to that reported from Nairobi, Kenya and contrasting with analogous data for the USA. The age for optimal protection against measles mortality by a single dose of vaccine in this group of children is nine months. Maternal antibody exerted a negative effect on measles antibody titre in vaccinees beyond the age at which it blocked the response so that the infants of mothers with the higher titres themselves had lower titres. A separate effect of immunological immaturity on titre of the response could not be demonstrated in children over six months of age.