RESUMEN
In Thailand, the morbidity rate of measles has declined since measles vaccination was included in the National Immunization Programme. A measles outbreak affected 41 infants in an orphanage in Bangkok during September-October 2000 prompted an investigation to study the epidemiological distribution, assess vaccine coverage and vaccine effectiveness. The attack rate was 66 per cent, among infants aged 6-12 months in two separate rooms. Sixty-three per cent of the 41 cases were less than 9 months old. Measles vaccine coverage among infants over 9 months was 45 per cent due to delay in immunization caused by mild illnesses of the infants and the vaccine effectiveness was 91 per cent (95%CI 42%-99%). Inefficiency of the surveillance system to early detect and respond to the outbreak was observed. A catch-up immunization program, close supervision for surveillance and immunization systems and an increase of measles vaccine coverage to more than 95 per cent in this and other orphanages in Thailand were recommended.