Measles Booster Shots and You?

In 2022, there were 941 reported cases of measles in the World Health Organization’s European region. Over just the first 10 months of last year, according to an alarming bulletin the W.H.O. issued in mid-December, there were more than 30,000.

This is the kind of spike — a 3,000 percent increase — that looks implausible in headlines. And it appears even more significant compared to recent years, when efforts to limit Covid also resulted in almost entirely eliminating measles in Europe in 2021. (In a lot of places, we sort of accidentally eliminated the spread of flu, too.)

But as the year drew to a close, the European measles outbreak kept growing. Through December, case numbers in the region eventually reached over 42,000, and although the largest outbreaks were in countries most Americans regard as pretty remote (Kazakhstan, Kyrgyzstan and Russia), there is also a vicious surge in Britain, which may look plausibly to us as the canary in a coal mine. There, in just one of England’s nine regions, the West Midlands, 260 cases have been confirmed and dozens more suspected, in a country which, as a whole, recorded just two cases as recently as 2021.

Almost certainly, the virologist Rik de Swart of Erasmus University Medical Center in Rotterdam tells me, these official case totals are significant underestimates. But as intimidatingly large as they are, the outbreaks are not in any way surprising to infectious disease specialists, who have been warning that long-term declines in vaccination rates were creating the possibility of a huge resurgence. “This is precisely what is expected,” the epidemiologist Michael Mina, formerly of Harvard, told me. The epidemiologist Bill Hanage, also at Harvard, lamented it to me as a “chronicle of an outbreak foretold.”

There have been worrying outbreaks, too, in the United States, where a few dozen cases, nationwide, is sufficient to command federal public health attention. But it is striking — especially given pandemic panic about America’s exceptional-seeming resistance to vaccination — that the world’s most high-profile post-Covid measles surge has come not here but in Europe.

Almost since the beginning of the pandemic, public health officials worried that efforts to limit transmission of Covid could interrupt vaccination programs for other diseases, particularly in the developing world, and almost since the start of Covid-19 vaccination programs, they’ve worried that rising vaccine skepticism, particularly in the United States, might permanently damage acceptance of previously “routine” vaccines — for measles, mumps and rubella, for instance.

Vaccination skepticism and polarization, though, are just one story to tell about the pandemic in the United States. Here, many more people spurned mRNA shots than in comparable peer countries, a vaccination shortfall which probably explains perhaps several hundred thousand additional American deaths. But in absolute terms, coverage of the most vulnerable was, nevertheless, really quite high, with nearly 95 percent of people 65 and older receiving at least two doses of Covid protection, according to the C.D.C.

As the country turned its focus away from Covid, you could see reasons for concern in falling rates of routine vaccination. But the rates are falling pretty slowly, all things considered, despite the politicization of vaccination.

Between the 2019-2020 and 2021-2022 school year, the C.D.C. found that the share of American kindergartners up to date on M.M.R. vaccines fell from 95 percent to 94 percent and then to 93 percent. These declines are not insignificant — 7 percent unvaccinated means perhaps 60,000 more vulnerable kindergartners than 5 percent unvaccinated — but in a country of more than three million kindergartners it also isn’t a landscape-shifting cliff drop. For 2021-2022, only nine states exhibited declines of 2 percent or larger.

Americans often think of vaccine hesitancy as primarily ideological, but demographic, socioeconomic and educational drivers may be even more powerful, and as best we can measure them, the ideological drivers are also moving relatively slowly, too. The percentage of Americans saying that vaccination should be required for all children in school fell from 82 percent in 2019 to 71 percent in 2022, according to the Kaiser Family Foundation, but the number of children claiming an exemption to existing mandates has risen much more slowly, to just 2.6 percent that same year.

In 2016, according to Pew, 88 percent of Americans said that the benefits of the M.M.R. vaccine outweighed the risk, against 10 percent who said it didn’t. The numbers were exactly the same in 2019, on the eve of the pandemic, and exactly the same again, after it, in 2023. (My colleague Jessica Grose wrote about these numbers and the stories we tell ourselves about them last summer.)

In Europe, the W.H.O. attributed the recent outbreak mostly to falling vaccination rates, too, though there the declines were of roughly the same scale: for the first dose of the M.M.R. vaccine, from 96 percent to 93 percent between 2019 and 2022, and for second doses, from 92 percent to 91 percent. In Russia and Kazakhstan, official coverage rates were even higher. True rates may be lower, and in certain demographic pockets perhaps much lower — a factor that determines spread risk much more than overall coverage numbers. Nevertheless, in all of these countries, including ours, a vast majority of people are vaccinated against diseases like measles and a vast majority of them continue to vaccinate their children against them, too.

The problem is, it doesn’t require vaccination levels to fall by half, or even by a quarter, to produce outbreaks of a disease like measles, which in populations that have never been exposed to it before is many times more infectious than Covid was at first. (Early alarmist estimates of its “reproduction number” suggested that every new case of SARS-CoV-2 might lead to 3.8 new cases; each new case of measles leads to 12 to 18.) Even somewhat imperceptible declines in vaccination coverage can open up once-unthinkable vulnerabilities — and not just for measles. Experts have long called the disease a “tracer” virus that, by virtue of its incredible infectiousness, exposes gaps in vaccination coverage and in the health system that other diseases may soon exploit, too.

This is the big lesson of the European outbreak. Measles is a well studied and analyzed virus, to which we owe much of foundational wisdom about infectious disease. But we don’t really know the exact level of protection that’s needed to prevent transmission in the real world or just keep it at bay, only a sense of the ballpark range — and that even very small drops in coverage from even very high levels of protection can produce quite gnarly out-of-control transmission.

“The metaphor I use for this is, it’s like playing Jenga,” said the biologist Matthew Ferrari of Penn State. “You pull the blocks out and every time you pull a block out that tower is closer to falling, but you don’t know which pull is going to make it fall until it falls. That’s why it’s a game.”

Population immunity is complicated — not just a simple matter of vaccination rate but age structure and levels of social mixing and many other factors. But pull enough blocks and the tower will collapse. “And it’s a nonlinear response — measles going from tiny little outbreaks to continual spread and persistent spread that lasts for longer than a year,” said Ferrari.

This isn’t to say that something precisely like the European outbreak, or worse, is looming in the United States, since chance plays a significant role in the timing of and scale of disease spread, and since there are pretty significant differences in the underlying vulnerabilities of the two places. In the United States, for instance, measles is officially “eliminated,” as it is in much of the Western Hemisphere; in Europe the record is much patchier, with measles circulating in some countries somewhat regularly.

Because the decision not to vaccinate is somewhat more ideologically driven in the United States, the unvaccinated may be less geographically concentrated, leading to more resilient herd immunity than in Europe. In parts of London, as many as 25 percent of children enter school unvaccinated — not just because of anti-vax sentiment but more likely because of simple lack of access. But here, too, Mina said, the groups of unprotected children are growing, “and once the pockets start to get big enough that they merge into each other — bam! We may have major outbreaks of 10,000 people or more infected here as well.”

And the initial illness is not the only cost of a measles infection. As the pandemic has worn on, some researchers have wondered about the possibility of immunological damage from Covid infections. But we know that measles really does diminish if not erase the immunological capacity of many survivors for as long as several years, making them vulnerable to a wide variety of infections and potentially susceptible again to diseases they thought they’d put behind them long ago. In very rare cases, many years after an initial infection, measles can even lead to a incurable degenerative neurological disorder called subacute sclerosing panencephalitis, which can produce sudden loss of language and balance, typically in adolescents who got sick with measles but recovered as young children, and will almost always eventually lead to coma and death. In the Netherlands, de Swart tells me, doctors are dealing with several of those cases today from a large-scale 2013 outbreak in what’s known as the Dutch Bible Belt.

Across Europe and the United States, health care infrastructure means that individual infections are considerably less scary than they might be in other parts of the world — with fatality rates as low as one in a thousand even for the vulnerable young, de Swart estimates, as opposed to perhaps one in a hundred in lower-income countries. In an outbreak in a refugee camp, he says, you could see death rates as high as one in five. “So we’ve seen big outbreaks in Europe, and we’ve seen smaller outbreaks in the U.S.,” he said, “but the number of severe disease cases, let alone the number of fatalities, is fairly limited.”

As a result, he says, the recent panic about a measles revival in the global north is a bit of a red herring for him. “Worldwide this infection still causes more than a 100,000 deaths every year,” he said, with outbreaks concentrated in sub-Saharan Africa, where the pandemic hampered already inadequate vaccination, and global measles deaths are up 43 percent year-on-year. “The real problem is not in the U.S., it’s not in Europe, it’s in the low-income countries. That’s where this virus is really a killer virus.”

LONDON — A serious outbreak of measles in England could grow to tens of thousands of cases, health experts there have warned, as Europe grapples with a spike in the highly contagious disease.

The U.K. Health Security Agency said Friday that since October, there have been 216 confirmed cases and 103 probable cases in the West Midlands region, an urban part of England centered on the city of Birmingham, where around 80% of the cases were recorded. That’s higher than last year’s total of 209 measles cases and the 2022 tally of 53.

Last year, the government warned that a measles outbreak in London could lead to between 40,000 and 160,000 cases there if the vaccination rate did not improve. The rate in England has been falling for years due to misinformation and declining community health budgets.

Around 89% of children in England have received their first measles, mumps and rubella (MMR) vaccine dose by age 2, according to the state-run National Health Service — down from 93% a decade ago. The World Health Organization considers 95% the necessary threshold to maintain herd immunity.

A British information campaign is now urging people to ensure their children get the vaccination.

British lawmaker Maria Caulfield, who was previously the minister of state for health, laid bare the scale of the challenge when she told the House of Commons on Monday that more than 3.4 million children under 16 are not vaccinated against measles.

In Europe overall, Hans Kluge, the World Health Organization’s director for the region, warned Wednesday that there had been 42,200 measles cases across 41 countries in 2023 — a nearly 45-fold increase from the 941 recorded the previous year. He said last month that nearly 21,000 people had been hospitalized.

A crisis is also building in central Asia, where more than 13,600 cases were recorded in 2023, the majority among unvaccinated children under 14, the WHO said.

Three U.S. states have also recorded measles cases in the last month. Philadelphia has confirmed at least eight locally acquired cases, in addition to one “imported” case that prompted a health alert in December. Camden County, New Jersey, confirmed a case on Jan. 13, then Georgia health officials confirmed the state’s first case in four years soon after: an unvaccinated resident in Atlanta.

Measles is most common in children. The disease is characterized by a red, blotchy rash that usually follows a high fever, cough, runny nose and red, watery eyes. Around 1 in 5 unvaccinated people with measles are hospitalized, and up to 3 out of 1,000 children with measles die from complications such as pneumonia or swelling of the brain, according to the U.S. Centers for Disease Control and Prevention.

The MMR vaccine is offered to children in Britain starting at 12 months, with a second dose shortly after they turn 3. Children in the U.S. get their second dose between 4 and 6 years old. Two shots are 97% effective, according to the CDC.

“Even if you reach them, it’s really difficult to keep such high levels of vaccination sustained over a long period,” said Helen Bedford, a professor at University College London’s Great Ormond Street Institute of Child Health. “You get there, the disease goes away, people think, ‘Oh, well, the disease has gone away; I don’t need to vaccinate.’”

Several other factors have fueled England’s vaccination challenges, experts said. One is that uptake remains especially low among low-income and more ethnically diverse groups, according to a 2021 NHS study in southeast England.

“It’s poor people, people who are highly mobile and don’t stay in one place,” said Azeem Majeed, professor of primary care and public health at Imperial College London. “In regards to messaging, the NHS needs to be more proactive on this.”

On Thursday, in an effort to reach non-English speakers, the local council in the borough of Brent released a video about measles in Romanian.

A second factor is a now-discredited study published in 1998 that falsely claimed the MMR vaccine was linked to autism. The paper was partially retracted in 2004, but by then vaccine uptake had dipped to 81%. The study was fully retracted in 2010 and its author, Andrew Wakefield, was removed from the U.K. medical register.

Thousands of children born in the late ’90s and the early 2000s are now unvaccinated adults.

“It’s this combination of low uptake about 20 years ago, so you’ve got lots of young adults that are susceptible, and then over the years an accumulation of susceptible people, particularly in some parts of London,” Bedford said.

However, Bedford doesn’t consider vaccine hesitancy and the spread of conspiracy theories to be the main problem. British parents’ confidence in vaccines is as high as 90%, according to a 2022 study.

“The anti-vaccine movement is very, very small, but it has a very loud voice,” she said. “So I think it’s important not to get too hooked on that because there are lots of things we can do. And if we just focus on anti-vaccine, it’s much more difficult to know what to do.”

Instead, Bedford pointed a finger at two other factors: a reduction in community nurses and reforms made to the NHS — namely the 2013 decision to spread the responsibility for vaccines across several agencies rather than one.

What’s more, she said, there is a lingering opinion among some Britons that measles is a trivial childhood illness, which is a dangerous view.

“In a best-case scenario, measles is a nasty disease that makes children feel very ill. But of course there is a recognized significant complication rate, with ear infections, pneumonia, inflammation of the brain and, yes, it can kill you,” Bedford said.

This week, doctors’ clinics in the West Midlands area urged patients not to turn up unannounced if they suspect they have measles: “Call ahead, that way if you do have measles — you won’t pass it on to others — it can be a fatal disease if someone has a weak immune system,” a public information flyer said.