York Region has declared the measles outbreak in Thornhill officially over as of Nov. 19.
The outbreak, which began on Sept. 4, resulted in nine confirmed cases. No new linked cases have been reported since Oct. 4.
A York Region media release on Nov. 24 said that the Vaughan (Thornhill) outbreak was unrelated to a separate Ontario-wide measles outbreak that began last fall. Just under a year later, the provincial government officially declared the Ontario-wide outbreak over on Oct. 6.
The province-wide outbreak resulted in 2,375 cases, including 51 pregnant individuals and nine infants born with measles. One infant died as a result of their infection.
Measles is still spreading in other provinces, where a person could transmit the virus back to Ontario and York Region.
Dr. Fareen Karachiwalla from York Region Public Health said that York Region’s partnerships with primary care, schools, and other community partners helped contain the Vaughan outbreak.
“We are very relieved and lucky that our local outbreak did not get larger or increase in severity,” she said. “Measles is the most contagious communicable disease we have, and we’ve seen some significant consequences in other situations and jurisdictions.”
Measles is a highly contagious viral infection that spreads via airborne transmission. Initial symptoms may include a fever, cough, runny nose, or red, watery eyes. A blotchy red patch then appears on a patient’s face three to seven days later before expanding to the rest of their body.
The MMR vaccine – short for measles, mumps, and rubella – is 97 per cent effective at preventing measles after two doses.
On November 10, 2025, the World Health Organization officially revoked Canada’s measles elimination status. This is a significant loss after 27 years of maintaining this designation. Measles elimination meant that a country or region did not have an outbreak for at least 12 consecutive months.
A 2022 study concluded that less than 95 per cent of Canada’s population was vaccinated against measles, which is necessary to prevent an outbreak – a concept known as herd immunity.
“The measles vaccine is one of the most effective interventions modern medicine has seen,” Karachiwalla said. “So, the loss of this status is a stark reminder of the impact of vaccine hesitancy and declining immunization rates.”
The MMR vaccine is free and available to those who are eligible or overdue. If you do not have a primary care provider, York Region Public Health offers measles vaccination appointments for individuals aged 12 months to 55 years old.
For more information or to book a vaccination appointment visit york.ca/Measles.
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