Ontario's chief medical officer of health says six infants have been born with congenital measles since an outbreak began last fall, adding they were infected in the womb through mothers who were not vaccinated.
Dr. Kieran Moore says these infants recovered, but their infections could have been prevented if their mothers had been vaccinated and protected from contracting measles.
Congenital measles can result in severe complications, including inflammation of the brain and death.
On Thursday, Moore announced an infant born prematurely and infected with measles died in southwestern Ontario.
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He says the infant also faced other serious medical complications unrelated to the virus.
In an interview with The Canadian Press, Moore says 40 pregnant people have been infected with measles in Ontario, and only two were vaccinated.
Moore suggests unvaccinated pregnant people isolate if they live in a community with active measles cases. Health officials have reported more than 2,000 cases in the province since the outbreak began in October.
The measles mumps and rubella (MMR) vaccine is not recommended once a person is pregnant because it contains a live virus that could theoretically be transmitted to the fetus.
The National Advisory Committee on Immunization recommends unvaccinated pregnant people get one dose of intravenous immunoglobulin within six days if they are exposed to measles.
However, Moore said that message faces hurdles similar to those around vaccine hesitancy.
“Some people, if they don't want a vaccine, they may not want the immunoglobulin either. That may be a philosophical choice,” Moore said Friday.
In an editorial published Monday in the Canadian Medical Association Journal, Dr. Catherine Varner argues pregnant people are "bearing the burden" of Canada's measles outbreak.
“Pregnant people are often at higher risk than the general population in infectious disease outbreaks. As such, they cannot be an afterthought in preventive strategies and health-care systems’ responses,” Varner writes.
Moore said the vast majority of pregnant people in Ontario are fully vaccinated against measles.
“It's only a very small subgroup of people who have chosen not to get vaccinated who are having the complications,” he said.
"I know some will concentrate on the glass being half-empty. You know, to have that level of protection in the face of the risks globally, I think is quite an accomplishment.
"I'd love to have 100 per cent, but we have to work with these communities that have chosen not to be vaccinated, and that is a long and difficult conversation that I think all of our health-care workers are dedicated to having."
This report by The Canadian Press was first published June 9, 2025.
Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.
