Medical experts urge vaccination after more than 100 measles cases confirmed in Ontario this year
'Highly contagious' respiratory illness was once declared eliminated in Canada in 1998
Two Hamilton-area medical experts are reminding Canadians that being vaccinated is the best way to prevent getting sick with measles or spreading it to other people.
Dr. Sarah Khan, infectious diseases physician at McMaster Children's Hospital, and Dawn Bowdish, a professor in the Department of Medicine at McMaster University, spoke with CBC as measles cases in Ontario continue soar.
In 2025 so far, the number of cases has already surpassed the number from all of last year. The new cases bring this year's total to 119 that were confirmed in a lab and 23 that are probable, according to Public Health Ontario data as of Feb. 26.
The Grand Erie region has more than half of Ontario's cases — that includes the City of Brantford as well as Haldimand-Norfolk and and Brant counties.
Of the total cases in Ontario, 18 children were hospitalized, none of whom were immunized.
Highlighting the importance of vaccination, Khan said measles is one of the most infectious diseases known to humans.
LISTEN | Dr. Sarah Khan talks about the importance of vaccination to combat measles:
"If you were in the same room as someone even for a very short period of time, there's like a 90 per cent chance you will get this infection if you don't have immunity," Khan said on CBC Radio's Fresh Air.
"This is the important part around how do we get our population immune? Because of how infectious measles is, we need a herd immunity of more than 95 per cent to prevent outbreaks like these.
"Unfortunately we've fallen below that number and this is why we're seeing a more rapid spread and these larger outbreaks occurring," Khan added.
The infectious diseases physician said herd immunity occurs when the majority of the population have received two doses of vaccine or have had measles previously, which may have happened in young childhood for the older members of the population.
"The important point is for people to know their immunity status, find out if they are vaccinated or not, and if they are not, they need to go and get their booster or get their two doses in," Khan said.
"[In 1998] we were able to eradicate this virus in … Canada. Unfortunately, we are seeing a resurgence simply because of decreased vaccine uptake. We had this under control and we risk getting out of control if we cannot bring that vaccine status or getting that herd immunity back up."
Access to vaccines part of the challenge in Canada: expert
Like Khan, Bowdish said given the "highly contagious" nature of measles, more than 95 per cent of the population has to be vaccinated in order to maintain the status of not having measles endemic in Canada.
"What we're seeing, especially in the province of Ontario, is that there's pockets of people who have very, very low immunization rates, and that means it can spread like wildfire in those communities," Bowdish said on The Current.
LISTEN | Prof. Dawn Bowdish talks about the resurgence of measles in Canada:
But the low vaccination rate may be partly because of access, not necessarily vaccine hesitancy, Bowdish said. "Even if people have concerns over COVID vaccines or influenza vaccines, Canadians generally do trust childhood vaccines," she said.
"It's availability, it's the family doctor crisis, it's the not being able to get vaccines at a time that works with their work schedule... The Canadian situation is one in which outright refusal is actually comparatively rare. It's access and availability and convenience that tend to be the drivers of this fallen vaccination rates."
Bowdish said measles has "a really long" asymptomatic period of approximately five to 21 days, and that means "a person can be walking around breathing out the virus and somebody could pick it up before they even know they're sick."
Cases of measles have also been reported this year in B.C., Manitoba and Quebec.
A child who wasn't vaccinated died in a measles outbreak in rural West Texas, state officials said on Feb. 26, the first U.S. death from the highly contagious — but preventable — respiratory disease since 2015.
ABOUT THE AUTHOR
With files from CBC Radio's Fresh Air, The Current and The Associated Press