Ontario is grappling with a significant surge in measles cases, as an outbreak continues to spread, primarily among unvaccinated individuals.
According to Public Health Ontario, the province has recorded 372 cases since the outbreak began on October 28, 2024—an increase of 195 cases since the last update on February 27. Health officials are calling this a “sharp increase” driven by transmission among unvaccinated children and teenagers.
Dr. Christine Navarro, a public health physician at Public Health Ontario, warned that more cases are likely in the coming weeks.
The majority of new cases are linked to a larger outbreak originating in New Brunswick, which has since spread to Manitoba. The rise in cases has led to 31 hospitalizations in Ontario, including a child who required intensive care.
Among those hospitalized:
- 30 patients were unvaccinated
- One patient’s vaccination status is unknown
- Seven infections occurred in pregnant individuals (five unvaccinated, two with two vaccine doses)
Navarro noted that “breakthrough” cases, where vaccinated individuals contract measles, do occur but are much rarer.
“We expect some cases in those who have received one or two doses of the vaccine, but the overwhelming majority of cases are among the unimmunized,” she explained.
While breakthrough infections do happen, they are usually mild due to vaccine protection. Severe complications from measles can include pneumonia, brain inflammation, and death. In pregnant individuals, the virus can lead to miscarriage, premature labor, and newborn infections.
Declining Vaccination Rates Raise Concern
One of the most alarming trends in Ontario is the drop in routine immunizations. Public Health Ontario data shows that in the last school year, only 70% of seven-year-olds were fully vaccinated against measles—a significant decline from pre-pandemic levels.
The National Advisory Committee on Immunization recommends a 95% vaccination rate to maintain Canada’s measles-free status.
The measles-mumps-rubella (MMR) vaccine is typically administered in two doses:
- First dose: between 12 to 15 months old (or as early as 6 months if exposure risk is high)
- Second dose (booster): between 4 to 6 years old, with added protection against chickenpox
More Public Health Units Reporting Cases
Measles cases have now been confirmed in 11 public health units across Ontario. Residents are being urged to check their immunization records and remain alert to potential exposure sites, including:
- Restaurants
- Grocery stores
- Community centers
- Toronto Pearson International Airport
On March 13, Toronto Public Health confirmed a case of measles with potential exposure at Pearson Airport and on an Air Canada flight on March 2. Officials advise anyone who may have been exposed to monitor for symptoms until March 23.
With the outbreak escalating, health officials continue to stress the critical role of vaccination in preventing further spread.
