[Measles epidemic in a school population. Effectiveness of the vaccine].

OBJECTIVE

To describe the distribution of the illness according to the school students' measles vaccination status and to assess its effectiveness.

DESIGN

Analytical study of a retrospective cohort.

SETTING

Two schools within the Base Health Area of San Leonardo de Yagüe, Soria.

PATIENTS

410 school students between 3 and 14. 314 were included in the study sample.

MEASUREMENTS AND MAIN RESULTS

The overall vaccination rate was 81.8% and was higher among lower age groups. The overall incidence rate was 18.5%; 9.7% in those vaccinated and 57.9% in those not vaccinated. The incidence rates increased with age, 5.5% for the 3-6 and 24.5% for the 11-14 age groups. Vaccine effectiveness was measured by Relative Risk (5.9) and Attributable Fraction (83.2%), with a statistically significant association between non-vaccination and the occurrence of measles.

CONCLUSIONS

As measles vaccination is highly effective, it would be worthwhile to increase vaccine coverage to 93.5-96%, so that group immunity within a community can be attained and so transmission of the disease be avoided.