Determining infants' age for measles vaccination based on persistence of protective level of maternal measles antibody.

The present study was conducted over a period of one year to find the right time for measles vaccination when maternal antibody titer in infants was decayed rendering them susceptible to wild virus infection. Blood samples were collected from the cord of new born (147), 2-5 months (47) and 5 to 7.5 months (24) of age. The mean measles IgG antibody titer detected in cord blood at birth (0 months) was 348.8 mlU/mL which steeply decreased to 155.6 mlU/mL by the age of 2-3 months. After that the fall in antibody becomes relatively slower and decreased to 101.6 mIU/mL by the age of 3-5 months and 38.8 mlU/mL by the age of 5-6 months and to 19.2 mIU/mL between the age of 6 to 7.5 months. The fall in antibody level with the advance of age was statistically significant (p < 0.001 ). Majority of the subjects (97.6%) exhibited protective level of antibody at birth. But only a little above one-quarter (25.5%) of them persisted the protective level between the age of 2-5 months and none had protective level from 5 months onwards.