Maternally derived measles immunity in children of naturally infected and vaccinated mothers.

Measles antibody titres were established in three groups of infants: children of vaccinated mothers, children of unvaccinated mothers and neonates born after different gestational periods. Lower measles antibody titres were observed in children whose mothers had been vaccinated, and these decayed to undetectable values earlier than in children whose mothers had not been vaccinated, and were assumed to have had natural measles. Lower measles antibody titres were observed in premature neonates than in full term babies, and these lower antibody levels will presumably decay to undetectable values earlier than in full term neonates. These results, if confirmed by larger studies, would indicate an earlier optimum age for vaccination against measles than the currently recommended 13-15 months for two groups in order to reduce the risk of natural infection before immunization. These groups are children in a highly vaccinated population whose mothers have a low measles antibody titre and premature children (defined as having a gestational period of less than 37 weeks).