[A measles epidemic in an adequately vaccinated middle school population]

To assess the extent of a measles epidemic in a secondary school.Retrospective and questionnaire investigation.Secondary school, Bilthoven.Questionnaire followed by laboratory testing for measles and other infectious diseases with exanthema.The response rate was 99% (935/949 pupils, aged 12-21 years, vaccination rate 92%). Seventy-seven students underwent laboratory investigations. Measles virus was isolated in 2 suspected patients. Thirty-three of 37 patients with clinical or laboratory criteria of measles had been vaccinated. Complications of measles were not detected. Infection was also detected in patients with relatively few or atypical symptoms. The protective efficacy of measles vaccine could be determined because the attack rate of the school population was less than 5%.Primary failure of the measles vaccine might be the cause of the minor epidemic but the results do not cast doubt on the efficacy of the current measles vaccination programme.