Measles is back and anti-vaccine sentiment is to blame

Measles was supposedly eradicated in Canada more than a quarter century ago. But today, measles is surging.

Public Health Ontario recently announced that there have been 173 cases in the province in the past two weeks and 350 cases since autumn 2024. Many cases have required hospitalization. Last year, a child died.

The cause of this resurgence is declining vaccination rates.

Measles is extremely infectious. One person with the measles is likely to infect nine out of 10 of their unvaccinated close contacts. To prevent its spread, we need 95 per cent of the population to be vaccinated.

Anti-vaccine sentiments

Our research examines why parents have hesitated or refused to vaccinate their children. Anti-vaccine sentiment is often linked to a now thoroughly discredited 1998 study that suggested a link between the MMR (measles, mumps and rubella) vaccine and autism.

But our research on the anti-vaccine movement in Canada from the 1970s to the early 2000s suggests that parents’ concerns about vaccines started much earlier than that study, and that parents worry about far more than autism.

To address anti-vaccine sentiment, we need to listen to parents’ concerns and make it easy for them to get their children vaccinated. We also need to persuade them of the benefits of vaccination, not just for their own children, but for their family members, friends and fellow citizens.

The anti-vaccine literature is not anti-science. It is filled with statistics and references to scientific studies, although the facts are often wrong. Parents who read this literature need more than the simple reassurance of experts that vaccines are safe and effective. They need to be shown evidence and have confidence that their concerns are being taken seriously.

One argument that appeared frequently in the anti-vaccine literature is that rates of infectious disease had fallen before the introduction of vaccines.

While mortality from infectious diseases declined well before vaccination, vaccines played a vital role in further diminishing the toll of infectious disease. Diphtheria is largely unknown today, but before the introduction of widespread vaccination in the years between the First and Second World Wars, it killed hundreds of Canadian children every year.

Another common argument was that vaccines are ineffective. This argument was often used with respect to the measles vaccine. Because some people are inadequately vaccinated (receiving only one shot for example, instead of two), and because the vaccine is not perfect, there will be some cases of measles even in vaccinated people. Fortunately, these people tend to have milder cases.

Anti-vaccine texts frequently contain long lists of scary-sounding ingredients in vaccines, similar to what we see for highly processed foods. Thimerosal (ethyl mercury used as a preservative) attracted the most attention. Thimerosal is no longer used in childhood vaccines in Canada.

The anti-vaccine literature is deeply skeptical about the profit-making motivations of pharmaceutical companies and often mentions past disasters such as the thalidomide scandal that saw thousands of children born with shortened limbs.

While this is not the only example of inadequate safety testing of new drugs, it is clear that the MMR (measles, mumps and rubella) vaccine, used since the early 1970s, has a long safety record and has played a vital role in reducing deaths and illness from the measles in Canada and abroad.

Anti-vaccine literature also stressed that there were natural ways of building immunity that could take the place of vaccination. We see this today with claims by United States Health Secretary Robert F. Kennedy Jr.

Kennedy claims that poor eating habits are behind the spread of measles in the U.S. This is extremely dangerous. Even the healthiest, best-fed child can get extremely sick with the measles. Not all parents can afford nutritious food. And some children can’t be vaccinated because of medical conditions, leaving them extremely vulnerable.

Tragedies of the past

Anti-vaccine parents see vaccines as one of the dangers of our modern, polluted world, and worry that vaccines might have risks that have not yet been recognized. While there are risks with any medical technology, the benefits of vaccines far outweigh the possible dangers.

A century ago, parents mourned the gruesome deaths of children with diphtheria, which caused a membrane to form across the child’s throat, slowly strangling them to death.

Mortality from the measles declined in the first half of the 20th century, but in 1945, there was still one measles death for every 100,000 people in Ontario.

Parents today have little memory of these tragedies, but sadly, they could return. Indeed, a powerful article recently published in the Atlantic Monthly profiled a father who had just lost his six-year-old child to the measles.

Along with scholars like sociologist Jennifer Reich, who has studied contemporary anti-vaccine parents, we see anti-vaccination sentiment as part of a larger societal trend towards individualism. Parents think about what’s best for their own child, rather than thinking about what’s best for their community.

At a time when Canadians are bonding together to fight the tariff threat from the U.S., it would be wonderful if we could also come together to fight the scourge of infectious diseases, including measles. The best way to do this is vaccination.

This is a corrected version of a story originally published on March 18, 2025. The earlier story said “Public Health Ontario recently announced that there have been 195 cases in the province in the past two weeks and 372 cases since autumn 2024” instead of “Public Health Ontario recently announced that there have been 173 cases in the province in the past two weeks and 350 cases since autumn 2024.”

This article is republished from The Conversation under a Creative Commons license. Read the original article.