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Large community mumps outbreak in Manitoba, Canada, September 2016-December 2018
Yichun Wei1, Krista Wilkinson2, Richard Rusk3
1Epidemiology and Surveillance, Manitoba Health, Seniors and Active Living, Winnipeg, MB.
Background:
After routine mumps immunization programs were implemented in Manitoba in the 1980s, incidence was low, with 0-9 cases of disease annually. In September 2016, a mumps outbreak began in fully vaccinated university students in Winnipeg, Manitoba.
Objective:
We describe the investigation of this province-wide mumps outbreak, which lasted between September 2016 and December 2018. We present the details of public health measures implemented and challenges encountered. Possible contributing factors to the sustained transmission are also provided.
Methods:
Probable and confirmed cases of mumps were investigated by public health departments using the investigation form developed for this outbreak. Confirmed mumps cases were linked to the provincial immunization registry. An outbreak response team planned and implemented control measures across the province.
Results:
The outbreak began in vaccinated university students in September 2016 and spread across the province. Activity was high and prolonged in the northern remote areas. By the end of 2018, 2,223 cases had been confirmed. All age groups were affected, and incidence was highest among people aged 18-29 years. Two-dose coverage of mumps-containing vaccine in confirmed cases was close to 70%.
Conclusion:
This prolonged outbreak revealed a large vulnerable population likely resulting from under-vaccination and waning vaccine-induced immunity in the absence of natural boosting from exposure to mumps virus. It is important to maintain high two-dose coverage with mumps-containing vaccines. A third dose of mumps-containing vaccine in future outbreaks may be considered.
Insights
A prolonged mumps outbreak in Manitoba affected vaccinated individuals, highlighting potential waning immunity and under-vaccination. Maintaining high vaccine coverage is crucial, and a third dose may be considered for future outbreaks.
Area of Science:
- Epidemiology
- Immunology
- Public Health
Background:
- Routine mumps immunization in Manitoba led to low disease incidence since the 1980s.
- A significant mumps outbreak commenced in September 2016 among fully vaccinated university students in Winnipeg.
Purpose of the Study:
- To investigate a province-wide mumps outbreak from September 2016 to December 2018.
- To detail public health interventions, challenges, and factors contributing to sustained mumps transmission.
Main Methods:
- Investigation of probable and confirmed mumps cases using a standardized form.
- Linking confirmed cases to the provincial immunization registry.
- Implementation of province-wide control measures by an outbreak response team.
Main Results:
- The outbreak, originating in vaccinated students, spread province-wide, with prolonged high activity in northern remote areas.
- A total of 2,223 mumps cases were confirmed by the end of 2018, affecting all age groups.
- Confirmed cases showed approximately 70% two-dose mumps-containing vaccine coverage.
Conclusions:
- The outbreak identified a large vulnerable population due to under-vaccination and waning vaccine-induced immunity.
- Maintaining high two-dose mumps-containing vaccine coverage is essential.
- Consideration of a third mumps vaccine dose for future outbreaks is recommended.
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