Measles is a preventable infectious viral disease. Since 1985, India has been administering a single dose of measles vaccine to all infants at 9 months of age. This age was chosen to balance the disappearance of maternal (transplacental) antibodies with the increasing risk of developing measles. Thus infants are expected to get protection against measles by acquired maternal measles antibodies derived trans-placentally from the mother for the first 9 months of life. Thereafter vaccine-induced antibodies are expected to protect infants. Seroconversion after measles vaccination does not take place as long as maternal measles antibodies persist in the infant. However, it is widely recognized that a substantial proportion of measles infection (10 to 15%) can occur among infants before the age of measles vaccination. Further, two small cohort studies done in our institution confirm that the majority of infants lose maternal antibodies by six months of age, making them susceptible to measles.This argues strongly for anticipating measles vaccination to an earlier age. However, such early vaccination has the risk that residual maternal antibodies (even if insufficient to protect infants) can neutralize the antigen in the vaccine, rendering vaccination ineffective. Therefore, a careful balance has to be chosen so that low levels of circulating maternal antibodies do not interfere with infants' response to vaccination. However, there is no prospective study in Indian infants to determine the seroconversion and sero-protection rate of earlier vaccination.