Do you need another MMR vaccine amid outbreaks? Here’s what you need to know

A dose of the measles, mumps, and rubella (MMR) vaccination awaits the next patient during a vaccine clinic at Southwestern Public Health in St. Thomas, Ont. on Tuesday, March 4, 2025. THE CANADIAN PRESS/ Geoff Robins (Geoff Robins/THE CANADIAN PRESS)

With measles cases on the rise in Canada, many people are asking whether they should or can get a third or “booster” dose of the measles-containing vaccine. Here’s what you need to know about vaccine recommendations, recent outbreaks, side effects, and more.

Should I get a third dose of the measles vaccine? How many MMR shots do you need in a lifetime?

Health officials say a third dose is not recommended at this time. Health Canada says for those who’ve never had measles, one dose provides up to 95 per cent protection. Two doses are nearly 100 per cent effective. If you’ve already received two doses, you’re considered fully protected.

How do I know if I had the measles vaccine?

Canadians will have to ask their doctor for records if they don’t have their own paperwork. Depending on when they were born, they are more or less likely to have had one or both doses of vaccine. You may also be able to request a blood test to confirm.

What if I only got one dose as a child? Should I get another now?

You might have to depending on when you were born and whether you’ve had any immunity testing, according to Health Canada. This is what Health Canada says:

• Adults born before 1970 are generally considered immune due to natural infection;
• Those born between 1970 and 1980 may have received only one dose;
• People born after 1980 are more likely to have received two doses through routine childhood immunization or school-based catch-up campaigns;
• Adults born in 1970 or later who plan to travel to high-risk countries should ensure they’ve had two doses;
• Those born before 1970 who are travelling may be advised to get one dose if they’re not already immune; and
• Susceptible health-care workers, travellers to destinations outside of Canada, and military personnel should receive the vaccine, regardless of year of birth.

What types of measles vaccines are used in Canada?

Canada offers two types of measles-containing vaccines: MMR (measles, mumps, rubella), and MMRV (measles, mumps, rubella, varicella or chickenpox).

What are the measles vaccine side effects?

Common side effects include swelling, soreness or redness at the injection site. One to three weeks after vaccination, some people may develop a mild fever, rash, joint stiffness or gland swelling. These usually resolve in a few days.

Serious reactions are very rare but can include allergic responses like difficulty breathing, facial swelling or hives. Seek medical help immediately if this occurs.

Can you still get measles after vaccination?

It’s rare, but possible, health officials say. Health Canada says the efficacy of a single dose of the MMR or MMRV vaccine, if given on the usual schedule, is between 80 and 95 per cent, with a second dose bringing that to “almost 100 (per cent).”

The U.S. Centers for Disease Control says about three per cent of people who receive both doses may still get measles if exposed. In these cases, the illness is usually milder, and they’re less likely to spread the virus to others.

How does measles spread?

Measles is highly contagious. It spreads through the air when an infected person coughs or sneezes, even if they’ve left the room up to two hours earlier. It can also spread through direct contact with respiratory secretions.

What are the symptoms of measles?

According to Health Canada, the symptoms of measles can include fever, cough, runny nose and red, watery eyes. It may then progress to include a rash that “looks like red spots and blotchy patches” that starts on the face then spreads across the body.

Complications include ear infection, pneumonia, diarrhea, and in rare cases, respiratory failure, encephalitis (inflammation and swelling of the brain), and even death.

Who is most at risk?

Unvaccinated people and those who haven’t previously had measles are at highest risk, especially if they travel to areas where the virus is circulating. Complications are more likely in people who are pregnant, immunocompromised, or under five years old.

Should I consider a measles party for my child?

No. Health experts strongly advise against intentionally exposing children to measles. The virus can lead to serious complications including pneumonia, deafness, encephalitis and even death. These gatherings have also been linked to worsening outbreaks in the past.

What should I do if I’ve been exposed?

If you believe you’ve been exposed and are unvaccinated or unsure of your status, contact a health-care provider immediately. You may be eligible for a vaccine dose or antibody treatment to reduce the risk of illness.

What’s happening in Canada now?

As of mid-April 2025, more than 1,000 measles cases have been reported in Canada, most linked to an ongoing outbreak that began in New Brunswick and spread to Ontario, Alberta, Manitoba, Prince Edward Island and Quebec. Some cases have been traced to travel or contact with recent travellers. Countries of travel for cases exposed outside of Canada include Cambodia, India, Kenya, Mexico, Pakistan, Romania, South Korea, Uganda, and Vietnam.

Bottom line:

Vaccination remains the best protection against measles, The Public Health Agency of Canada says. If you’re unsure of your vaccine history, speak to a health-care provider or request a blood test to confirm your immunity.

With files from CTV News’ Kendra Mangione