Public Health Update for Clinicians: Response to Measles Risk

Alert Date
Location
Windsor-Essex County

The Windsor-Essex County Health Unit (WECHU) would like to provide an important update in collaboration with the Ministry of Health in response to the continued multi-jurisdictional measles outbreak and increased measles community exposures and transmission in Windsor-Essex County (WEC). As of May 6, 2025, 1,440 measles cases (1,221 confirmed, 219 probable) have been reported in Ontario related to the outbreak1. This continued spread is due to continued exposures and transmission among individuals who have not been immunized, with majority of cases occurring in western Ontario1. Approximately 87% of cases occurred among unimmunized individuals and approximately 7% with unknown immunization status.

As part of the outbreak response, public health units in western Ontario, specifically Chatham-Kent, Grey Bruce, Lambton, Middlesex-London, Waterloo, Wellington-Dufferin-Guelph, Windsor-Essex, Southwestern, Grand Erie, and Huron Perth that continue to see increased transmission and community exposures have been asked by the Ministry to immediately implement the following measles outbreak immunization strategy, if not already in progress.

Please note the following guidance regarding immunization for measles2:

  • Measles outbreak recommendations for individuals who live, work, travel (e.g., family visit), worship, or spend time in affected regions and communities with active measles cases and where the risk of exposure in the community is higher:
    • Infants (six to 11 months): Should receive one dose of the measles, mumps, rubella (MMR) vaccine. Two additional doses are required after the age of one year.
    • Children (one to four years): Children who have received their first dose of MMR vaccine are encouraged to receive a second dose as soon as possible (at a minimum of four weeks from the first dose).
    • Adults (18+ years) born on or after 1970: A second dose of MMR vaccine is recommended.

Note: Any combination of varicella-containing vaccines requires an interval of 6 weeks between doses. 

The WECHU continues to ask that if clients of your practice or health care facility contact your office requesting appointments for post-exposure doses of MMR vaccine, it is important for those doses to be provided within the recommended post-exposure timelines to be effective. The WECHU will continue to guide susceptible contacts about the timelines within which a dose of vaccine can be administered, and we encourage providers to plan whenever possible to support this immunization. For information on infection prevention and control recommendations refer to Public Health Ontario’s Measles IPAC Checklist for Clinics and Specimen Collection Centres.

Additional guidance from the ministry is expected in the near future. Health Care Providers (HCPs) in WEC are invited to attend a lunch and learn hosted by the WECHU and the Medical Officer of Health, Dr. Aloosh on Tuesday, May 13, 2025. An invitation will be emailed shortly.

For questions or concerns, please call 519-258-2146 ext.1420 during regular office hours, and 519-973-4510 during after-hours and weekends. You can also visit our website. 
 
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