RESUMEN
Due to the recent finding that most infants in developing countries have lost maternal antibody for measles before nine months of age, immunization of infants younger than the recommended age of nine months would help reducing the incidence of measles in these endemic areas. We conducted a trial of Edmonston-Zagreb measles vaccine which is the strain that may be more immunogenic in young infants than the widely used Schwarz strain. Forty-five infants with mean age of 25 weeks received a dose of Edmonston-Zagreb vaccine. Antibody levels were measured, using plaque neutralization test, before and about 3 months after vaccination at which mean age was 38 weeks. The seroconversion rate was 89%. Only two infants (4.4%) had immunity before vaccination. Fifteen infants (33.33%) reported some adverse reactions including fever (13.33%), rhinorrhea (8.89%), rash (4.44%) and local reactions (22.22%). All of the reactions resolved spontaneously. We conclude that Edmonston-Zagreb measles vaccine is efficacious and safe in infants aged under nine months.