Born In The 1970s? You Might Need An MMR Booster

Nearly eight months into a measles outbreak that has seen hundreds of cases nationwide, numbers continue to rise. As of last month, 2,755 cases have been reported in 2025, with most numbers concentrated in Ontario and Alberta. 

Understandably, health officials are worried. Measles, also known as rubeola, is highly contagious and can be especially dangerous to children, the elderly and people with compromised immune systems. For nearly 30 years, vaccination rates had all but eliminated the disease in Canada, but if numbers don’t start to trend downwards, we  could lose its elimination status by fall. 

If you’re worried about measles, the best thing you can do is ensure that you and your loved ones are inoculated from the disease–and, if you were vaccinated as a kid, confirm with your doctor whether you might benefit from an MMR booster.

What is the measles vaccine and how does it work?

The measles vaccine is part of a combined vaccination that protects against measles, mumps, rubella—and depending on the type of vaccine—varicella (chickenpox) virus as well. It uses an attenuated (i.e. live, but weakened) form of the virus to expose the body to its antigens, teaching the immune system how to recognize and fight against it.

The vaccine is administered in two doses, typically in infancy and then again in early childhood. It’s 97 per cent effective against the disease once both doses are administered, at which point an individual can be considered immune for life. With more than 50 years’ worth of study on the distribution of this vaccine among populations across the globe, we also know that it’s incredibly safe.

Do you need a booster for the measles vaccine?

There are a few factors to consider, says Dr. Donald Vinh, an infectious disease specialist and medical microbiologist at the McGill University Health Centre in Montreal. People born before 1970–and therefore before MMR vaccinations were routine in Canada—were likely infected with measles and have immunity as a result. “Those people are generally not recommended to have a booster dose, unless they're in high-risk settings,” he says, such as schools, hospitals or long-term care homes, or, if they travel outside of Canada frequently, and particularly if they are heading to an area with a known measles outbreak.

People born after 1980 are likely to have been administered both doses of the vaccine. But if you’re in what Dr. Vinh calls the “grey zone”—i.e. you don’t know your vaccination status, don’t have your vaccination records, only received one dose, or don’t know if you’ve ever had measles—it’s best to talk to your GP about getting a booster, providing there’s no medical reason why you can’t (more on this in a minute).

Are there risks to getting an MMR booster if you’re unsure of whether you need one? 

“If you have no immunocompromising condition, or you are not currently pregnant,” says Dr. Vinh, “there is no risk in receiving another dose, even if you are already protected.”

Why can’t pregnant women take the vaccine?

Vaccines that contain live attenuated viruses generally aren’t recommended for women during pregnancy, which makes ensuring vaccination status a priority prior to getting pregnant. 

There’s two main reasons for this, the first being during the pregnancy itself. “Measles can lead to severe and sometimes life-threatening complications during pregnancy, affecting both the mother and the unborn baby,” says Dr. Vinh, and Ontario’s measles outbreak has seen an increase in hospitalizations among pregnant patients who have been infected with the disease.

The second is immunity transference. “Up until the first six to 12 months of age, babies are dependent on the antibodies they've received from their mother during pregnancy. If the mother does not have antibodies to measles at the time that she is pregnant,” says Dr. Vinh, “then nothing gets transferred to the baby during pregnancy, and the baby is vulnerable to disease when they encounter measles.” 

Are there other high-risk groups when it comes to measles? 

Infants, young children and immunocompromised people are at particular risk—particularly those who can’t receive the vaccine if their immunocompromising condition prevents them from doing so. “However, they can still be protected through herd immunity—meaning if at least 95 per cent of the people around them are vaccinated against measles,” says Dr. Vinh. So when you’re protecting yourself from measles, you’re doing the same for others.