Skip navigation

Ensure staff measles vaccinations up-to-date, reduce exposure risk, how to test and more during Ontario measles outbreak

Ensure staff measles vaccinations up-to-date, reduce exposure risk, how to test and more during Ontario measles outbreak

Article

Halton Region Public Health: Office of the Medical Officer of Health

Quick facts

  • Ontario is experiencing an outbreak of measles, concentrated in southwestern Ontario.
  • As of March 26, 2025, 557 cases of measles (464 confirmed, 93 probable) have been reported in Ontario in association with this outbreak.
  • Outbreak cases have now occurred in 13 Public Health Units and unrelated, sporadic cases have been identified in several other health units, including Peel and Hamilton.
  • Ensure that you, your staff and patients are up to date with their measles vaccinations. If staff are not up to date on their measles immunizations, they may need to isolate if they are exposed.
  • There are additional vaccine recommendations for people who live, work, travel, worship, or spend time in affected regions.
  • Consider measles in the differential diagnosis if a patient presents with a fever, respiratory symptoms, conjunctivitis, and/or a maculopapular rash that begins on the face and spreads downwards (typically appears 3-5 days after onset of prodromal symptoms). This is particularly important if they have a history of recent travel to areas with increased measles activity, and/or are not fully vaccinated.
  • Immediately report suspected/confirmed cases to Public Health by calling 311 or 905-825-6000. Do not wait for lab confirmation.

Key messages for healthcare providers

Diagnostic testing

  • Immediately report suspected/confirmed cases to Public Health by calling 311 or 905-825-6000. If needed, Public Health will facilitate specimen transport to Public Health Ontario (PHO).
  • All physicians can test for measles. If you suspect measles, reduce exposure risks by:
    • Placing your patient in a single room (with negative air flow if available).
      • The patient should wear a mask and immediately be placed in a single closed room upon arrival to clinic and be assessed at the end of the day.
    • Post-visit: Keep the room unused for 2 hours. Advise patient to self-isolate until results are available.
    • Send patients to a hospital ER only if clinically indicated and after calling ahead to minimize high-risk exposures in hospital settings.
  • Specimen collection:

Measles immunization

  • Continue to provide immunizations to susceptible patients as per the Ontario Publicly Funded Immunization Schedule and the Canadian Immunization Guide.
  • Ensure that measles-containing vaccines are readily available in your office. Vaccines can be ordered from Halton Region Public Health through the online Vaccine Order Form.
  • Efficacy of a single dose of measles vaccine, given at 12 or 15 months of age, is estimated to be 85% to 95%, and is almost 100% with a second dose.
  • Current Ontario recommendations are that children receive two doses of an appropriate measles-containing vaccine:
    • First dose on/after their first birthday.
    • Second dose at 4 to 6 years old.
  • Additional publicly funded recommendations:
    • Health care workers or military personnel: Two doses of the measles vaccine are recommended regardless of year of birth.
    • Born in 1970 or later: Should have at least one dose of the measles vaccine. A second dose is recommended for travellers to risk areas and post-secondary students.
    • Born before 1970: considered to be immune to measles based on probable exposure earlier in life. One dose of the measles vaccine is recommended for travellers to risk areas and post-secondary students.

Outbreak-related immunization recommendations

  • The following is advised for individuals who live, work, travel (e.g., family visit), worship, or spend time in affected regions and communities with measles cases and where the risk of exposure is higher. This currently includes the Grand Erie, Southwestern and Huron-Perth Public Health Units (see map below) and will be reassessed as needed:
    • Infants (six to 11 months): Should receive one dose of the measles, mumps, rubella (MMR) vaccine. Two additional doses continue to be recommended after the age of one year.
    • Children (one to four years): Children who have received their first dose of measles-containing 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.
  • Advise patients and/or their parents/guardians to report all immunizations they receive to Public Health via online reporting or by calling 311

Additional resources

Attachments

This memo included the following attachment(s):

  • Measles resources for healthcare professionals (Halton Region)
  • Measles factsheet (Ontario College of Family Physicians)

If you did not receive them via email, please contact doctors@halton.ca to request a copy.

Back to Physician Notices and Updates
Top