The world is losing major ground in the fight against measles

A child in the UK died from measles this month. A baby in Canada died from measles in June. Two children in the US have died from measles this year. But it didn’t have to be this way. Measles is a preventable disease – yet we have regressed to a point where we are acting as though it isn’t. And if we don’t act quickly to right the ship, we could see cases of other preventable diseases rise as well.

The US is in the throes of its largest measles outbreak since it eliminated the virus in 2000. More than 1300 cases have been confirmed so far – the highest number in 33 years. And it isn’t alone. In 2024, Europe reported its highest caseload in more than 25 years, doubling that of the year prior. Last year, there were almost 3000 confirmed cases in England, the highest number since 2012. Meanwhile, Canada has had more than 3800 reported measles cases this year – more than the previous 26 years combined.

It is an unprecedented situation. Most of these countries haven’t witnessed measles outbreaks this large since the 1980s and 90s, back when most people only received a single dose of the measles, mumps and rubella (MMR) vaccine. After implementing a two-dose regimen – which is about 97 per cent effective at preventing measles – cases plummeted, and many countries declared measles eliminated around the turn of the century.

That is why this moment is so alarming. Measles is resurging not because we don’t know how to stop it, but because we are no longer trying. “We have never been in a situation where [the spread of measles] was driven by vaccine hesitancy,” says Tina Tan at Northwestern University in Illinois. “This is uncalled for because we have safe and effective vaccines to prevent this from occurring.”

Herd immunity against measles, in which most people in a community are protected, occurs when more than 95 per cent of a population is vaccinated. That threshold was met with the two-dose regimen among US children in kindergarten – which usually starts at age 5 – during the 2019-2020 school year. But four years later, coverage dropped below 93 per cent.

Yet national averages don’t tell the full story. Vaccination rates began waning in many US counties well before 2019. In fact, Peter Hotez at Baylor College of Medicine in Texas and his colleagues flagged declining coverage in Gaines county, Texas – the epicentre of the country’s current outbreak – back in 2016. Then, MMR vaccination rates for the county were hovering around 95 per cent in kindergarteners. Now, they are less than 77 per cent. “So we kind of saw this coming for at least a decade,” says Hotez. “You really have to go down to the county level to see the horror unfold. That’s where you see pockets of very low vaccination rates.”

A similar story is playing out across the world. In Canada, the percentage of 2-year-olds with at least one MMR dose fell from almost 90 per cent in 2019 to less than 83 per cent in 2023. In Alberta, Canada, a hotspot in the country’s current outbreak, rates fell from more than 83 per cent in 2019 to about 80 per cent in 2024 – and some populations in the region report rates as low as 32 per cent.

Meanwhile, less than 85 per cent of 5-year-olds in the UK received both MMR doses in the 2023-2024 school year. In fact, among the 48 member countries of the Organisation for Economic Cooperation and Development (OECD), the UK ranked 30th in measles immunisation rates, while Canada ranked 39th, New Zealand 32nd and the US 4th. Hungary topped the list with almost 100 per cent coverage, whereas Romania sat at the bottom with about 20 per cent.

Vaccine hesitancy is driving these trends, and the movement has become so prominent that one of its most well-known figures, Robert F Kennedy Jr, now leads the US Department of Health and Human Services (HHS). Kennedy, who denies being anti-vaccine, has falsely claimed the MMR vaccine carries the same dangerous risks as measles, such as encephalitis and blindness. The risk of side effects is substantially greater with measles infection. For instance, 1 in 1000 people who contract measles will develop encephalitis – a dangerous form of brain inflammation – in comparison with only about 1 in 1 million children who get vaccinated.

Still, Kennedy has encouraged people to get themselves and their children vaccinated against measles. During a Fox News interview in March, he said the US government is ensuring anyone who wants a vaccine will get one.

It may already be too little, too late. While measles cases are starting to taper off in the US, Hotez fears they could ramp up again in a couple months when children head back to school. The outbreak is already into its seventh month, and if it lasts for a full year, the US will lose its measles elimination status. The UK has already dealt with this. After eradicating measles in 2016, the country lost its status two years later, before finally regaining it in 2023.

But Hotez worries the current outbreaks are only the tip of the iceberg and vaccine hesitancy will chip away at progress made against other preventable illnesses, such as polio and pertussis. “I don’t think this stops at measles,” he says.