Ontario measles cases rise amid growing concern about spread among unvaccinated individuals
Measles cases continue to rise in the country's most populous province, with Public Health Ontario reporting Thursday there has been more than 100 new cases of the highly contagious disease in the last week.
New figures released by Public Health Ontario show since the beginning of 2025, a total of 440 measles cases (357 confirmed and 83 probable) have been reported in Ontario, as of this Wednesday.
The new figures represent an increase of 120 cases (103 confirmed and 17 probable) since the release of its epidemiological summary last week which noted nearly 200 cases.
The spread of measles is a growing concern in Canada, which stands in stark contrast to the country's status in 1998, when the disease was deemed to be eliminated. Public health specialists credit the measles, mumps, rubella vaccine for preventing spread of the disease in the last the decades.
But they are increasingly worried about what is unfolding: Ontario now has the highest number of cases it has seen in more than a decade. There have also been recent cases in New Brunswick, Quebec and Alberta. Additionally, there is a global resurgence of measles, such as in Europe. There have also been outbreaks in the U.S. in New Mexico and rural parts of Texas.
Health officials highlight accelerated MMR vaccine guidance in measles outbreak areas of Ontario
Canada's Chief Public Health Officer, Theresa Tam, has said the majority of measles cases reported domestically are among unvaccinated people, many of whom are children and infants.
Since last October, a total of 470 measles cases (361 confirmed and 109 probable) have been reported. The cases are associated with an outbreak that has occurred in 11 public health units. Last October, a travel-related case in New Brunswick led to measles cases in Ontario.
Ontario's Chief Medical Officer of Health, Kieran Moore, said last week that the majority of cases in the province are among unvaccinated individuals.
Dr. Moore recently issued a memo with new immunization recommendations that apply to individuals who live, work, travel, worship or spend time in the areas covered by the Grand Erie and Southwestern public health agencies near Hamilton and London respectively. Both are seeing measles outbreaks.
He advises that babies aged six to 11 months should receive one dose of the MMR vaccine and two additional doses are still recommended after turning one. Children who are aged one to four who have received a dose of the measles vaccine should receive a second dose as soon as possible and at least four weeks after the first shot. Infants under six months are too young to receive a dose.
Measles is re-emerging in Ontario. Here's what you need to know to protect you and your family
Dr. Moore also said adults born in 1970 or later are encouraged to ensure they have received a second MMR shot. An immunization program for infants was introduced in 1983 when a single dose was given at one year of age. Public Health Ontario said a second dose was added in 1996.
Data indicate childhood vaccination coverage in Canada is sliding. A recent study published in the Canadian Journal of Public Health found a decline in measles vaccination coverage in children in 2023 compared with 2019.
Public Health Ontario said that measles cases in the province has been rare, owing to the successful elimination of measles in Canada in 1998 and high vaccination coverage.
It said the sharp increase in the number of outbreak cases and the geographic spread in recent weeks is because of 'continued exposures and transmission among individuals who have not been immunized.'
Measles is a highly contagious, airborne disease. It can result in serious health complications that, while rare, include respiratory failure, encephalitis, which is swelling of the brain, and death.
Symptoms for the disease include fever, cough, runny nose, red and watery eyes, and a rash that appears like red spots or blotchy patches. It can result in serious health complications that, while rare, include respiratory failure, encephalitis and death.
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