This story is part of CBC Health’s Second Opinion, a weekly analysis of health and medical science news emailed to subscribers on Saturday mornings. If you haven’t subscribed yet, you can do that by clicking here.
After an explosion of measles cases in Europe, medical experts say it’s just a “question of time” before outbreaks happen in Canada, thanks to high rates of global travel and low rates of vaccinations.
There were 42,200 measles cases across more than 40 European countries last year, the World Health Organization (WHO) announced this week — a more than 40-fold increase from 2022, which saw fewer than 1,000 cases. In December, the organization said there had been more than 20,000 hospitalizations and at least five deaths in the European region.
Globally, the situation is even grimmer, with a spike in infections in 2022 that included nine million known cases and 136,000 reported deaths, mostly among children.
The WHO said the rise in cases in Europe has accelerated in recent months, and the upward trend is expected to continue if urgent measures — like vaccination efforts — aren’t taken to prevent further spread of this potentially deadly infection.
“It’s not something that is mild,” said Dr. Kate O’Brien, a Canadian pediatric infectious diseases specialist and director of the WHO’s department of vaccines and immunization. “And it’s not something to be taken lightly.”
The risk in Canada
Canada eliminated measles back in 1998 through widespread vaccination programs.
Here, the vaccine is given to children as two doses of a combined shot that also protects against a combination of infections — either measles, mumps and rubella, or measles, mumps, rubella and varicella.
The annual case count remains small — only a dozen confirmed infections were reported country-wide in 2023 — and most cases are now acquired through travel outside the country.
But clinicians say outbreaks are still a risk. Canada, like many other countries, hasn’t hit the 95 per cent vaccination coverage required to prevent its spread.
“Measles is probably the most infectious human virus that is known, and as a result, in order to prevent measles infections, vaccination rates have to be really high in a community,” said O’Brien.
“What’s happened is, over the course of the pandemic, we’ve had a historic backsliding in the immunization rates around the world.”
Vaccination catch-up crucial
In Europe, the level of coverage with two doses of the measles vaccine dropped from 92 per cent in 2019 to 91 per cent by 2022, WHO data shows. Nearly two million infants also missed their measles vaccination in the first two years of the pandemic.
That means children are particularly at risk, clinicians say. Measles spreads easily through the air, leads to high hospitalization rates, and can cause a hacking cough, high fever and a prominent rash. In more serious cases, it leads to pneumonia, brain damage, and death in up to three out of every 1,000 children infected.
Infections can have wide-ranging and sometimes lifelong consequences, including blindness, deafness, or immune system impacts that leave people vulnerable to other infections.
In the U.K., where there have been hundreds of cases in recent months, including 127 reported infections in January alone, health officials also point the finger at “falling” vaccination coverage. One in 10 children start school in England without protection.
That’s similar to Canada. Federal data from 2021 shows that 79 per cent of children had two doses of measles, mumps, and rubella vaccine by their seventh birthday, down from 83 per cent in 2019 and 87 per cent in 2017.
That suggests close to two in 10 children hadn’t yet had their full set of shots — far from Canada’s target of 95 per cent coverage for that age group.
“Right now we’re underneath the level of immunization that we need to prevent onward transmission in Canada,” said pediatric infectious diseases specialist Dr. Charles Hui, who works with CHEO and the University of Ottawa.
Another study on population immunity in Ontario, published in 2019, found nearly eight per cent of blood samples had antibody levels below the threshold needed to ward off a measles infection. This suggested that immunity in some age groups may be waning “despite high vaccine coverage.”
And clinicians warn the situation is getting worse.
During the pandemic, when doctors’ offices were shut and public health units were tied up with COVID-19 screening and testing, routine immunization rates to protect infants and children from serious infections like measles plummeted across Canada.
“I think the answer is trying to do everything we can to optimize vaccination delivery and catch up all those people who missed vaccinations during that pandemic, ’cause there are a lot of them,” said Dr. David Pernica, division head of infectious diseases at McMaster Children’s Hospital.
“Most of these are people who would get their kids vaccinated if they had the time and means to do so.”
Normally, Pernica said, if someone doesn’t cough in our face or shake hands with snotty fingers then respiratory viruses don’t spread.
Measles, on the other hand, is so contagious that if an infected person walks into a store and another person who isn’t vaccinated comes in two hours later, they can still catch it.
Research suggests that one person with measles can spread it to an average of 12 to 18 others.
“It will be really critical for governments to provide the resources for public health and to primary care, to really do all they can to catch up all of those who have missed vaccinations, and to encourage vaccinations among those who have not yet decided to receive them,” he said.
The WHO’s O’Brien also stressed the safety and effectiveness of measles vaccines, which are roughly 97 per cent effective. “Over the past 20 years, we estimate that over 56 million deaths have been averted as a result of measles vaccination around the world,” she said.
Travellers bringing it home
Global travel remains a key concern for clinicians. In recent weeks, multiple Canadian public health alerts have been issued about possible travel-related exposures.
One confirmed case in a Saskatoon resident, who was infected through international travel, may have exposed others in various stores, a university campus and a hospital emergency room. Meanwhile, a confirmed case in the Windsor, Ont., area was linked to possible exposures at Toronto’s bustling Pearson International Airport.
“The 12 cases last year from Canada were all imported cases and that is concerning in and of itself,” Hui said. “But the concern would be if we import cases, and they come into contact with people who don’t have immunity, then we have transmission within Canada.”
He added it’s likely “just a question of time” before cases linked to travel abroad end up sparking an outbreak.
Dr. Shelly Bolotin, director of the Centre for Vaccine Preventable Diseases, urged families heading out of the country for spring break to plan ahead, even if they’re heading to places without outbreaks of measles or other vaccine-preventable infections.
“We can also get exposed at an airport,” said Bolotin, an associate professor at the University of Toronto’s Dalla Lana School of Public Health.
Normally, infants receive their first dose of measles vaccine at 12 months. But if a child is six months or older and going to a place where measles is circulating extensively, parents should discuss early immunization, she said.
Canada’s federal government has an ongoing global measles notice for travellers, noting outbreaks are “occurring in every region of the world,” leaving anyone unprotected at risk of being infected when travelling.
“That’s why it’s so important that every individual is protected against measles,” said O’Brien. “Because you don’t know where that exposure is going to come from.”