RESUMO
BACKGROUND: The aim of this study was to describe a mumps epidemic occurred among school children in Toledo, Spain, between 1993 and 1994 were vaccination was undertaken as control measure, and to estimate vaccine efficacy under field conditions. MATERIAL AND METHODS: Attack rates for vaccinated (at 15 months of age) and unvaccinated population were calculated. A retrospective cohort study was designed to estimate vaccine efficacy. RESULTS: A total of 19 outbreaks in different schools were declared. 216 cases and 4,059 contacts, between 10-17 years old, were investigated. The attack rate for the school population was 5.3%. By age, the highest attack rate was for those in the 12-13 age group (7.9%). Estimated vaccine efficacy was 76% (95% confidence interval 66-87%) for the whole study population: For children among 10-13 years old it was 87% (95% confidence interval 76-93%), and 46% (95% confidence interval 20-70%) for those aged 14-17 years. CONCLUSIONS: Vaccination is a good control measure in mumps outbreaks (the attack rate for the study population was 5.1%). Vaccine efficacy was high for the 10-13 age group and in agreement with the results of seroepidemiological studies.