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Objective : To assess the extent of a
mumps epidemic, reported to the school health service of Brugge during the
schoolyear 1995-1996.
Design :
Retrospective and questionnaire investigation.
Vaccination data from medical school records.
Methods : Schools that reported at least one case
of mumps disease between September 1st 1995 and June 30th 1996 were selected.
All parents received a questionnaire.
Results : The response rate was 83.6% (1843/2204
children, 878 boys and 965 girls, aged 3-12 years).
The vaccination coverage for mumps was 93%, but varied significantly between
schools (85.7%-95.9%) and age-group (88.7%-97.4%).
During the epidemic, 106 cases of mumps (44 boys and 62 girls) were reported
(5.8% of respondents; 5% of the boys and 6.4% of the girls), again with
striking inter-school variety (from 0.3% to 13.6% of the children being
infected).
Complications of mumps were reported in 2 children.
A correlation between immune status and illness was evident. 17.4% of the
unvaccinated, and 5.4% of the vaccinated children developed mumps during the
epidemic, while respectively 9.2% and 2.1% reported a former episode of mumps
disease. The calculated Odd's ratio for vaccinated versus unvaccinated children
to develop mumps disease during the epidemic was 0.23.
The longer the interval between immunization and contact with the virus, the
higher the risk to develop disease.
Conclusion : A vaccination coverage of 93% is not
enough to preclude minor epidemics of mumps. A secondary vaccine failure
might be the cause of the increasing risk by age to be infected.
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