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An assessment of mumps vaccine effectiveness by dose during an outbreak in Canada
Shelley L Deeks1, Gillian H Lim, Mary Anne Simpson
1Ontario Agency for Health Protection and Promotion, Toronto, Ontario. shelley.deeks@oahpp.ca
Background:
This investigation was done to assess vaccine effectiveness of one and two doses of the measles, mumps and rubella (MMR) vaccine during an outbreak of mumps in Ontario. The level of coverage required to reach herd immunity and interrupt community transmission of mumps was also estimated.
Methods:
Information on confirmed cases of mumps was retrieved from Ontario's integrated Public Health Information System. Cases that occurred between Sept. 1, 2009, and June 10, 2010, were included. Selected health units supplied coverage data from the Ontario Immunization Record Information System. Vaccine effectiveness by dose was calculated using the screening method. The basic reproductive number (R(0)) represents the average number of new infections per case in a fully susceptible population, and R(0) values of between 4 and 10 were considered for varying levels of vaccine effectiveness.
Results:
A total of 134 confirmed cases of mumps were identified. Information on receipt of MMR vaccine was available for 114 (85.1%) cases, of whom 63 (55.3%) reported having received only one dose of vaccine; 32 (28.1%) reported having received two doses. Vaccine effectiveness of one dose of the MMR vaccine ranged from 49.2% to 81.6%, whereas vaccine effectiveness of two doses ranged from 66.3% to 88.0%. If we assume vaccine effectiveness of 85% for two doses of the vaccine, vaccine coverage of 88.2% and 98.0% would be needed to interrupt community transmission of mumps if the corresponding reproductive values were four and six.
Interpretation:
Our estimates of vaccine effectiveness of one and two doses of mumps-containing vaccine were consistent with the estimates that have been reported in other outbreaks. Outbreaks occurring in Ontario and elsewhere serve as a warning against complacency over vaccination programs.
Insights
Measles, mumps, and rubella (MMR) vaccine effectiveness was assessed during an Ontario mumps outbreak. Two doses of the MMR vaccine showed higher effectiveness, highlighting the need for robust vaccination programs to prevent community transmission.
Area of Science:
- Epidemiology
- Immunology
- Public Health
Background:
- An outbreak of mumps occurred in Ontario, necessitating an evaluation of the measles, mumps, and rubella (MMR) vaccine's effectiveness.
- Assessing herd immunity thresholds and the coverage required to halt mumps transmission is crucial.
Purpose of the Study:
- To determine the vaccine effectiveness of one and two doses of the MMR vaccine during a mumps outbreak in Ontario.
- To estimate the vaccination coverage needed to achieve herd immunity and interrupt mumps transmission.
Main Methods:
- Confirmed mumps cases were identified using Ontario's Public Health Information System (2009-2010).
- Vaccine effectiveness was calculated using the screening method, with reproductive numbers (R(0)) ranging from 4 to 10.
- Data on immunization records were obtained from the Ontario Immunization Record Information System.
Main Results:
- Out of 134 confirmed mumps cases, 114 had vaccination information. 55.3% received one MMR dose, and 28.1% received two doses.
- One-dose MMR vaccine effectiveness ranged from 49.2% to 81.6%; two-dose effectiveness ranged from 66.3% to 88.0%.
- To interrupt transmission with a two-dose effectiveness of 85%, coverage of 88.2% to 98.0% is required, depending on the reproductive value.
Conclusions:
- The estimated MMR vaccine effectiveness aligns with findings from other mumps outbreaks.
- This study underscores the importance of maintaining high vaccination rates to prevent complacency and control mumps transmission.
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