Ontario’s Chief Medical Officer of Health is urging families to make sure everyone is vaccinated against the measles.

Ontario is in the worst measles outbreak in a decade.

A new report from Public Health Ontario, 277 confirmed infections and 95 probable cases have been reported across 11 health units in just the three months of 2025.

Between 2013 and 2023, there were 101 confirmed cases of the virus.

“This is the most measles cases Ontario has seen in over a decade. It is critical we work together to mitigate further spread of this vaccine-preventable disease,” he said in a news release.

Over 96 per cent of the cases are in people who have not been immunized and were exposed in their community or while travelling.

Today, Dr. Kieran Moore, Chief Medical Officer of Health, issued the following statement:

“Over the last several weeks, we have seen the number of new measles cases rise to 173 bringing the total number of confirmed cases in Ontario to 350 since 2024, including 31 hospitalizations.

“Vaccination is the most effective way to limit the spread of measles and protect yourself and your loved ones. The measles, mumps and rubella vaccine has been in use for more than 50 years and is proven to be one of the safest and most effective vaccines available,” Moore said. “All Ontarians should ensure themselves, and their children, are up to date on their vaccinations. Children who are fully immunized with two doses of the measles vaccine are nearly 100 per cent protected, with one dose estimated to be up to 95 per cent protective.”

Measles spreads easily among those who aren’t vaccinated and can lead to serious health issues including pneumonia, respiratory failure, swelling of the brain, and in rare cases, death.