Mumps in a boarding school: description of an outbreak and control measures.

BACKGROUND: The number of cases of mumps in the UK has increased during 2004-2005. Understanding why some people are more susceptible to mumps infection will help target vaccination and other control measures in the future. This paper describes a mumps outbreak in a boarding school in Scotland (October to November 2004). OBJECTIVES: To describe the characteristics of cases in a mumps outbreak; and to conduct a case-control study looking at the effect of previous measles-mumps-rubella (MMR) vaccination. DESIGN: Descriptive epidemiology. DATA SOURCES: Clinical, laboratory and surveillance data. SETTING: A private school with 600 boarding and day pupils. RESULTS: Fifty cases were notified to the public health department as having mumps. Twenty of the cases (40%) were confirmed virologically, all born between 1987-1991. A matched case-control study was conducted to explore the effect of prior MMR vaccination. Compared to no vaccine, MMR protected against mumps (odds ratio = 0.7), two doses offering best protection (odds ratio = 0.5), but the study was not large enough to detect a statistically significant difference. CONCLUSION: Some children and young people in the UK are currently incompletely vaccinated. This outbreak illustrates the potential of a mumps outbreak to disrupt the medical, educational and social life of a school. All children should be vaccinated with two doses of MMR vaccine before school entry. Children and young people born between 1979-1991 should be given the necessary additional dose(s) of MMR vaccine.