Background: Upon the detection of an excess number of cases of parotiditis in La Almolda (Zaragoza) a descriptive study of the epidemic was carried out with vaccination efficacy being quantified.
Methods: The definition and system of detection of the cases was established. To calculate the rate of infection the available demographic data were used as denominators. A study of retrospective groups was designed to calculate the vaccination efficacy including one group of vaccinated subjects and another of non vaccinated subjects. Age and viral contact were considered as inclusion criteria.
Results: Fifty-two cases of parotiditis were detected. The rate of infection in a population of under 30 years of age was 18.9%. The most affected age group corresponded to the interval of between 10-14 years of age with a specific rate of 46.5%. The risk of infection was greatest amongst public school students (RR = 5; p = 0.00015). Vaccination efficacy was 74.68%.
Conclusions: This study confirms the tendency that parotiditis affects older subjects during the prevaccination period. The vaccination efficacy found to be 74.68% was lower the efficacy determined from seroconversion studies.