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People born before 1970 are presumed to have been exposed to measles and likely to have some immunity, she says.  

But if people were born in 1970 or later and really have no idea if they were vaccinated, there is no harm in getting a dose of the measles, mumps and rubella vaccine to ensure they are protected as Canada continues to see a rising number of cases, Tam says.  

The exception is pregnant women, because the MMR vaccine isn't recommended during pregnancy as it contains live virus that could theoretically be transmitted to the fetus.  

Tam says it's vital for women of childbearing age to be vaccinated ahead of time because a measles infection can cause severe complications for both the mom and baby. 

She says if someone is already pregnant and thinks they might have been exposed to measles, they should talk to their health-care provider. 

Dr. Sarah Wilson, a physician with Public Health Ontario, says a blood test, known as serology, can be used to see if a pregnant person has antibodies to measles. 

"If there is uncertainty as to whether or not they've ever had an MMR vaccine, offering serology can be helpful to understand (if) this person (is) susceptible or not, so that if they are ever exposed to measles, they can very quickly be offered something called post-exposure prophylaxis to help reduce the risk of measles," Wilson said. 

But for most people who aren't sure of their vaccination status, getting a measles shot is preferable to getting a blood test to check for measles immunity, both Wilson and Tam said.

That's because the time lapse between getting the test and waiting for the results is a missed opportunity to get vaccinated sooner, they said.  

Tam said Canada has enough MMR vaccine to meet an increased demand for the shot. 

As summer approaches and people prepare to travel — both within Canada and to foreign countries — making sure you get a measles shot if you're unvaccinated or unsure should be part of the plan, Tam said. 

"Get ready to get vaccinated as early as possible, but I think the important point is if you really left it to the last minute, still go and get it," she said. 

"Even the last-minute immunization will offer some protection during that trip, but also it can protect you into the future."

Tam said being vaccinated against measles also helps protect others who can't be immunized, including pregnant women, children under six months old and some people who are immunocompromised. 

Babies usually don't get their first dose of MMR vaccine until they're 12 months old, but public health officials have lowered the age to six months in communities where there is a measles outbreak, including in southwestern Ontario. 

The devastating effects of the rise of measles in that hard-hit region became clear on Thursday, when the Ontario's chief medical officer of health announced a baby who was born prematurely and infected while in the womb had died. 

Dr. Kieran Moore noted that the infant also faced other medical complications unrelated to the virus.

Tam and Wilson both expressed their condolences to the grieving family.

"That was very sad news," said Tam. 

"I think it's telling us that we've all got to be very vigilant about measles in our communities."

This report by °µÍø½ûÇø was first published June 6, 2025.

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