My husband has a fun fact he pulls out whenever an icebreaker calls for one. The first time he ever flew in an airplane, he jumped out of it.

Yep, that’s right. He’d never set foot in a plane until, at 18, he decided to go skydiving. The desire to even consider doing that doesn’t just fail to resonate with me, it blows my mind. (Here’s hoping risk aversion is a maternally inherited trait and that my kids don’t get any ideas.)

Aside from my heart-stopping fear of heights, my hard pass on that plane daredevilry isn’t just about dying.Look at the data, and you’ll see that death from skydiving is exceedingly rare, on the order of one in 200,000 jumps. 

Injuries, however, are another story. In a single year, about one in 18 jumpers reported an injury that needed medical treatment. You can do everything right, land on your own two feet, and still come away with a shattered ankle or a blown knee and months of rehab. So when I imagine jumping, I’m not running a live-or-die calculation. I’m weighing the whole range of things that could go wrong, most of which land somewhere well short of death.

People weigh skydiving by more than the odds of dying. With measles, that instinct tends to slip. 

Serious measles repercussions—without death

Every time I share information about the measles, mumps, and rubella (MMR) vaccine, the same question comes back: Why do you care so much about a disease with a case-fatality rate of one or two in a thousand?

My answer comes in two parts.

The first is simple. Even one preventable death is one too many, especially when the thing standing between a person and that death carries an exceedingly small risk of its own. We’re weighing a vanishingly rare serious vaccine reaction against a disease that can kill, and that can do serious, lasting harm along the way.

The second part is the one that the “case-fatality rate” question doesn’t account for. It treats measles as a coin flip. Heads you live, tails you die, as if there weren’t an entire world of possibilities in between. There is, and that in-between is where measles does some of its most underappreciated damage.

Start with immune amnesia. When I talk to my immunology buddies about this, their eyes get wide. Measles doesn’t just make you miserable for a week or two. It infects immune cells, including the long-lived memory cells your body uses to recognize infections it has already beaten, and it wipes out part of that hard-won memory.

A 2019 study in Science found measles erased anywhere from 11% to 73% of children’s existing antibody repertoire, and even kids with mild cases lost about 20% on average. Your body can be left having to relearn defenses against infections it had already beaten, and it can take two to three years to rebuild what measles took.A statistical analysis of childhood mortality data suggests that, before the vaccine, this immune amnesia may account for as much as half of all childhood deaths from infectious disease, not from measles itself, but from everything a weakened immune system could no longer fight.

Measles … infects immune cells, including the long-lived memory cells your body uses to recognize infections it has already beaten, and it wipes out part of that hard-won memory.

Measles does obvious harm in the moment, too.About one in five unvaccinated people who catch measles in the United States end up hospitalized, often with pneumonia or dehydration. Utah’s ongoing outbreak has hospitalized 8% of its cases so far. In South Carolina, one hospital system that treated the outbreak there saw 16% of its confirmed patients admitted, two with encephalitis, or brain swelling.

In young children, measles can also cause swelling of the upper airway to the point of obstruction. Conducted during a 2025 outbreak,a Pediatrics study found this kind of stridor in about one in eight children with measles. Nearly 90% were hospitalized, and some needed intensive care. Not one of them died.Roughly one in 1,000 develops acute encephalitis, which can leave children deaf or with permanent intellectual disability even if they pull through.

SSPE, subacute sclerosing panencephalitis, is rare. But it’s a nightmare. Years after what looked like a full recovery, the measles virus can reactivate in the brain and begin a slow, relentless demolition: cognitive decline, seizures, loss of motor control, then death. There’s no cure, andit is almost always fatal. 

It was long thought to hit about one in 10,000 measles patients, but newer analyses put the risk far higher for the youngest measles patients, with some estimatesas high as one in 600 for babies infected before their first birthday. I cannot fathom the horror of a baby getting measles at 10 months old, everyone exhaling when she recovers, and then, six or eight years later when she’s in elementary school, it comes back to take her.

None of this shows up in a case-fatality rate. 

If only there were something to prevent it… 

The good news is that we have a tool against all of it. The MMR shot. For most people, its protection lasts a lifetime, and it covers the rare death, yes, but also the immune amnesia, the encephalitis, the hospital stays, the whole spectrum.

You might be thinking: if the vaccine works so well, why do we care whether other people get it?Two doses of MMR are about 97% effective, which means roughly three in 100 vaccinated people can still get infected if they’re exposed (a breakthrough case). When measles is rare, that 3% almost never comes up, because exposures rarely occur. 

But the more the virus circulates, the more often that gap gets tested, and breakthroughs add up. On top of that, some people can’t be protected by the vaccine at all: babies too young for the first dose, who are also the most vulnerable, and kids in cancer treatment. Aside from the math, public health folks have a nasty habit of caring about people we don’t know personally. 

What we don’t have are data on how [vaccine protection] holds up if measles becomes common again and vaccinated people are exposed over and over, year after year.

Two-dose protection has held up remarkably well for decades, outbreaks included. What we don’t have are data on how it holds up if measles becomes common again and vaccinated people are exposed over and over, year after year. For decades, low circulating virus meant that scenario rarely happened. That’s a gap in the evidence, not evidence of a flaw. Better to keep measles rare than to let the virus circulate freely and find out. 

I don’t avoid that plunge from a plane because I expect it to kill me. I avoid it because I don’t want any part of the spectrum of things that can go wrong once you jump. Measles deserves the same thinking. The vaccine doesn’t just protect against the worst case. It protects against everything in between. 

Dr. Steier is a public health scientist and scientific communicator. She is the founder of Unbiased Science, an organization that uses data visualizations, real-world analogies, and human voice to communicate complex scientific concepts for public understanding via multiple media modalities.

The opinions voiced in CIDRAP Op-Ed pieces are the authors’ own and do not necessarily represent the official position of CIDRAP.