“It’s heartbreaking to treat a sick child knowing their disease was entirely preventable”: A pediatrician on Ontario’s measles outbreak

Ontario has seen more than 600 diagnosed cases of measles since last fall, including a surge of about 100 cases last week. The outbreak—Ontario’s largest in almost three decades—has been traced back to a Mennonite gathering in New Brunswick in October of 2024, during which a group of largely unvaccinated people were exposed to the highly contagious illness.

Of course, vaccine hesitancy is hardly unique to Mennonites. Seventeen per cent of Canadian parents of two-year-old children are opposed to or uncertain about getting their kids jabbed, according to a 2022 report from the Public Health Agency of Canada. That statistic corresponds with Canada’s current measles vaccination rate of roughly 83 per cent, which is 12 per cent lower than the rate needed to reach community herd immunity and prevent outbreaks like the one we’re witnessing.
Here, Sarah Khan, a pediatrician and infectious disease specialist at McMaster Children’s Hospital, explains why she never expected to see measles make a comeback, how to protect your kids from infection and what to do if you spot symptoms of the disease.

Related: The Vaccine Truthers—Why parents shun life-saving shots

You specialize in pediatric infectious diseases. Did you ever think you’d see measles cases surge during your career? No, not at all, because it was eradicated. For all intents and purposes, we called it eliminated in Canada as of 1998. We had an effective vaccine that was rolled out across the board, and we achieved herd immunity—the amount needed to prevent outbreaks, which is 95 per cent for measles. More than 95 per cent of people were vaccinated, so we usually only ever saw sporadic cases related to travel. But, once people stopped seeing measles, they forgot how serious it can be. Social media has helped spread a lot of misinformation and beliefs about vaccines that have no valid supportive data. For example, the Lancet article that wrongly linked vaccines to autism in 1998 has been entirely discredited, and the doctor responsible for it was disgraced for falsifying data, but the misinformation spread just the same. More recently, we saw a rise in vaccine hesitancy during Covid, and because clinics were closed, many people missed their routine vaccines.

Do you remember the moment you first saw a kid with a rash and realized it was measles? No, because in practice, astute physicians have to put together the pieces well before there’s a rash. Initially, measles symptoms are often mild—cough, runny nose, maybe some pink eye. The patient could have diarrhea or dehydration. These symptoms won’t lead most people to think about measles, but at that point the patient is already infectious and is already spreading it. The red blotchy rash appears a few days later, usually starting on the face or trunk and spreading to the limbs from there. We need to recognize measles well before that stage to avoid complications. Pregnant people could go into pre-term labour or have miscarriages. Immunocompromised people are at risk of brain infection, loss of hearing, blindness, serious long-term neurological consequences or death. One in four measles patients requires hospitalization. Related: A U of T epidemiologist on the myth of immunity debt and the real reason everyone’s getting sick

My kid got sent home from school today with a sore tummy and a bit of a fever. Should I worry? If your child is vaccinated, you can take a big sigh of relief. The vaccine is extremely effective—anywhere between 96 and 98 per cent effective after two doses. Even a single dose is around 90 per cent effective. But, if the symptoms presented fit with measles, you should reach out to your doctor by phone—do not walk into a waiting room or hospital. They’ll ask the right questions and set you up for safe and efficient testing if necessary. The chance your child has measles is still very low, and there are a ton of other viruses going around. If your child isn’t vaccinated, if you’ve been exposed or just returned from travelling, definitely speak to your doctor before showing up to the clinic. They’ll need to prepare for your arrival by getting a room ready and making sure staff and other patients stay safe.

Is that a new protocol? Are you doing anything differently during this outbreak? We had a cluster of measles cases in Hamilton last year, so we put a lot of these measures in place then. We are aggressively screening patients as they arrive. That’s why we always ask about respiratory symptoms and about travel. We’ve added some new questions about measles exposure and immunity in light of this outbreak. Measles is highly contagious and stays in the air for up to two hours—long after the carrier has left the room. Nine in ten unvaccinated people who are exposed will become infected. The incubation period is anywhere between five days and twenty, so if you’re infected and are walking around unknowingly, the disease can spread rapidly. These windows of time make contact tracing especially difficult.

Related: This town has the lowest vaccination rate in Ontario

Things are changing every day, but can you tell me what’s going on with the Ontario outbreak right now? We’re in the thick of the outbreak that started last year. From 2013 to 2023, there were 101 cases of measles in Ontario. During Covid, there was a dip because no one was travelling. By 2023, there was a little jump, around 7 cases, which is pretty normal. In 2024, we saw 46 cases across Ontario. By the end of March, we hit nearly 600 cases in 2025 alone.

What does it feel like to see and treat a disease that you know is completely avoidable? More than anything, my focus is on treating the kid who is sick. It’s heartbreaking to see a child who is ill and to know that their disease was entirely preventable, though I don’t blame a parent in that situation. It’s a very tough spot to be in, to have to reconcile the fact that your beliefs and opinions have resulted in an illness in your kid, who didn’t get to decide or consent to your decision. Of course, I have conversations with parents about the importance of vaccinations, and some of those conversations go better than others, but by the time I enter the situation, the window of prevention is closed. These are conversations that should be had with primary care providers. We need to get real information out to people in a way that’s sensitive and meets their needs and answers their questions. Related: One Toronto mom’s epic battle with the anti-vaxxer mob

How hard is it to change someone’s mind about vaccinations? It’s difficult, but there’s been a lot of work done about how to approach vaccine hesitancy. Different approaches work with different people and populations—for some people, it’s about data; for others, it’s about a fear of reaction. Whatever it is, doctors can provide information, but it’s often trusted community leaders who are the most effective at reaching niche populations. I have seen people from other countries who have experienced measles talk strongly to their communities about the importance of vaccines. That, I think, is much more meaningful than anything I could have said. But there are people who are truly refusing, and there’s nothing anyone can say to change their minds. Still, we need to try. Every visit is an opportunity.

This interview has been edited for length and clarity.