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The quest to live forever has fascinated humans for millennia. The Epic of Gilgamesh, composed about 4,000 years ago, follows a king who searches the world for a plant that can restore youth, only to lose the plant to a thieving snake. The (likely apocryphal) story of Juan Ponce de León, who is said to have embarked on a search for the Fountain of Youth in the early 16th century, refuses to die—unlike its protagonist, who was killed along his journey.  

Today’s longevity-medicine movement is driven by the same aggressive desire for eternal youth as the mythic stories of old. But whereas in earlier times ideas about wellness could travel only as fast as the people who held them, today just about anyone with an internet connection can use social media and AI-generated graphics to sell medical advice in seconds. Despite a decided shortage of placebo-controlled trials in humans to support that advice, the business of longevity is booming, thanks in large part to sleek direct-to-consumer marketing delivered by health influencers with far more confidence than evidence. By 2030, $8 trillion might be spent annually on longevity-related products.

As a sports-medicine physician, I see the consequences of the modern longevity obsession up close. Patients arrive at my office convinced that the right peptides, cold plunges, or lab tests can meaningfully extend their lives. They’re almost certainly headed for disappointment—if not harm.

In many ways, the American people owe a debt of gratitude to the early champions of longevity medicine. Throughout the 20th century, Western physicians focused primarily on treating disease rather than preventing it. But over the past 15 years or so, a new generation of longevity-focused clinicians began emphasizing lifestyle changes such as sleep, exercise, and healthy diet as first-line strategies for disease prevention—not necessarily to extend life, but to improve health. More recently, private investment has poured into the field in pursuit of flashier claims about staving off death. Many longevity-focused clinics and influencers have drifted from prevention toward profit, selling an expanding menu of unvalidated treatments.

Some of the new advice is relatively harmless. Protein loading, for example, is unlikely to meaningfully extend one’s lifespan, but it is also unlikely to cause serious harm. Other trends are more concerning. I have seen patients experiment with drugs like rapamycin, an immunosuppressant medication prescribed for those who have undergone organ transplantation. Some health influencers claim, without convincing human-subject data to prove their point, that rapamycin slows cellular aging. Whether true or not, these claims have yet to be validated, but scientists do know that the side-effect profile of rapamycin includes an increased risk of infection and disease.

[Read: America has entered late-stage protein]

Other longevity enthusiasts are injecting or swallowing peptides, chains of amino acids that have been used in medicine for decades but are now becoming popular in their unregulated form. When prescribed by a physician, FDA-approved peptides such as insulin and GLP-1s can be remarkably effective. But no placebo-controlled human trials support the use of, say, “Wolverine” (scientific name BPC-157), a peptide that some influencers claim ramps up collagen production and aids tendon and ligament healing. Like many of the other non-FDA-approved peptides, anyone can order Wolverine online.

Along with supplements and drugs, excessive testing has become another pillar of the longevity movement. Apps, blood tests, and wearable devices purport to estimate customers’ “biological age” using metrics such as heart-rate variability, sleep scores, body composition, and biomarkers in blood. This type of “health score” does not predict how long a person will live, but it can provide a helpful snapshot of one’s current state of physiologic health and inspire healthy behaviors.

The bigger issue is more intensive screenings, especially full-body MRI scans, which many longevity clinics have marketed as tools to detect disease early and thereby extend life. Although this sounds like a good idea, the availability of screening has outpaced its clinical relevance. MRI scans routinely reveal anatomical changes that are a normal part of the aging process. Research suggests that the overwhelming majority of adults past middle age have tears or cartilage changes in their knees, or tendon injuries in their shoulders. Similarly, liver and kidney cysts are commonly seen on MRI scans, especially in people over 50, and most are of no clinical significance; they’re common enough that researchers have dubbed them incidentalomas. But when such findings show up on an MRI, the risk of unnecessary surgery or other treatment increases drastically. Once a liver lesion is seen on MRI, for example, the patient will likely be advised to get a liver biopsy, a procedure with a 2.4 percent risk of major medical complication.

[Read: GLP-1 envy was just the beginning]

Recently, I treated a 48-year-old man for a routine sports injury. Almost as an aside, he mentioned that he had undergone a full-body MRI as part of a longevity program. The scan revealed a small lesion in his prostate. His PSA, the validated screening test for prostate cancer, was normal. Still, he was referred to a urologist, who felt compelled to biopsy the lesion because it appeared on the scan. The biopsy was benign, but the procedure left my patient unable to sit comfortably for weeks. “I wish I’d never done the MRI,” he told me.

The irony is that modern medicine has already succeeded at what the modern-day longevity movement claims to offer. Over the past 150 years, human life expectancy around the world has more than doubled, to numbers that Ponce de León could hardly have dreamed of. Clean water, sanitation, antibiotics, and vaccines have done more to extend human life than any supplement stack ever could. Cold plunges and red lights may feel empowering, but there is little evidence that today’s biohacking tools meaningfully extend the maximum human lifespan.

A better—and more achievable—goal would be to extend healthy longevity, adding life to years instead of years to life. Scientists and doctors, for the most part, already know how to do this. Daily exercise and maintaining skeletal muscle volume as you age are among the most potent forms of preventive health care.

[From the January 2025 issue: America needs to radically rethink what it means to be old]

After decades of prescribing exercise as medicine to my patients, I tell them this: Move your body every day, and build muscles with weights or bodyweight exercises three times a week. Eat foods that you can recognize in nature. Prioritize sleep. Stay socially connected with community activities. Such a regimen may not enable you to cheat death. But it’s free. It’s evidence-backed. And it will help you live well right now.

A post on X claimed to be a simple message from the U.S. Department of Health and Human Services: Stay active; eat well. But the 90-second video it shared, called “Secretary Kennedy and Kid Rock’s Rock Out Work Out,” seems designed to be bewildering. Here was Robert F. Kennedy Jr. eating steak and doing preacher curls in his belted blue jeans and a pair of hiking shoes; and here he was again, stripping off his T-shirt to ride an exercise bike inside a sauna; and here he was a little later, strutting over to a cold-plunge tub (still in his blue jeans but with the belt removed); and here he went into the tub, sliding underwater in his dungarees.

Why was the HHS secretary bathing in a pair of pants? The video never provides an answer for this question, even as Kennedy plays pickleball, then mugs for the camera, then soaks in a Jacuzzi with a glass of milk, all while still in jeans. It’s just bizarre—a PSA that presumably has been dialed in by his staff to maximize its WTF effect. (The video has been viewed more than 13 million times and produced some 11,000 replies; HHS did not respond to a request for comment about the video or the jeans.) However his peculiar gymwear habit started, its present state is very clear: The secretary’s jeans are self-aware.

Kennedy’s proclivity for working out in belted denim long predates the knowing wink with which it’s now displayed. Take the summer’s “DOD-HHS Fitness Challenge,” for which Kennedy donned his favorite workout gear and did a bunch of pull-ups with Secretary of Defense Pete Hegseth. Or the viral clip of him from 2023, wearing jeans and boots and nothing else, squeezing out a final set on Venice Beach. I don’t believe that these show a man who lifts in jeans to maximize his clicks. I believe that they show instead a man who fits a waning archetype in fitness culture, a species that has for decades been endemic to the gym: Kennedy is a jeans guy.

I’ve worked out, off and on, for more than 30 years—and for all of that time, the jeans guys have remained a steady presence on the rubber floors. They are sometimes taciturn, sometimes chatty. They often pair their jeans with boots, as Kennedy will do, and with a T-shirt or a tank top or a hoodie. But lest you think he simply has no truck with any gym-specific gear, the jeans guy is sometimes spotted wearing padded lifting gloves, or a leather lifting belt across his Levi’s. At times, his social role will overlap with that of other weight-room regulars, not least of which is the gym grandpa, who hangs around and shoots the breeze and doles out tips on how to lift. However he appears, and however much he gabs, the jeans guy’s social status is the same: He’s an outsider. Rarely does one find a jeans guy paired up with a workout partner. “It’s usually like, ‘The jeans guy rides alone,’” Tolga Ozyurtcu, a historian of physical culture at the University of Texas at Austin, told me when I called him up to talk about this phenomenon.

Not everyone enjoys the company of the jeans guy. Some see him as a threat. Planet Fitness once made a point of banning denim in the gym, along with grunting, dropping dumbbells, and judging others. (Those who broke these rules could be punished with a “lunk alarm” and summarily kicked out.) But this discrimination feels as ill-considered as it is unfair: In my experience, jeans guys are harmless at the very worst, and at best, they add some needed color to a dreary landscape. In this way, the jeans guys are akin to other gentle curiosities, such as the shorts guys who alight on college campuses in wintertime, and the black chipmunks that scamper by from time to time in city parks.

What motivates the jeans guy? No one knows. He is, if nothing else, as inscrutable as a four-leaf clover. Ask him why he isn’t wearing shorts, and he will likely tell you that he chooses denim for efficiency. When Fox News’s Jesse Watters asked Kennedy in August to explain his favored workout gear, all Watters got was this: “Well, I just started doing that a long time ago because I would go hiking in the morning and then I’d go straight to the gym, and I found it was convenient, and now I’m used to it.” In the hope of getting more, I reached out to Ryan Calder, the fitness coach who spotted Kennedy on the incline bench in that viral video from 2023. Did Calder—who at the time was dressed, quite reasonably, in shorts—happen to ask Kennedy about his denim pants and boots? He did. “I asked him right then, you know, like, ‘So, you’re banging it out in jeans?,’” he told me. “And he’s like, ‘Yeah, man, this is my efficient way. I only have 30 minutes. I don’t spend time changing clothes.”

A jeans guy’s self-report must be taken with a grain of salt—maybe even he cannot really fathom why he lives the way he does. Kennedy’s is no exception to this rule. In public appearances, he is almost always in a suit and skinny tie, so adding a daily interlude in workout denim would hardly seem to be a way of saving time. His habit may be instead a product of the workout culture he imbibed during his youth. “The jeans guy, it’s a thing. It’s a very definitive thing,” Conor Heffernan, a fitness historian at Ulster University, told me. “It’s a trope we’ve had since the ’80s.” The power lifters of the time, some of whom were connected to the biker subculture, adopted a “rugged, spit-and-sawdust aesthetic” in the gym, he said. This included denim. During the same period, glitzy photoshoots for bodybuilders also featured jeans, to match the styles of the time. Heffernan brought up a famous photo of Lee Haney, the eight-time Mr. Olympia, flexing shirtless in a pair of jeans above a steamy manhole cover in New York City. Perhaps the older jeans guys of today—Kennedy himself is 72—are nothing less than living fossils.

Their aesthetic may have faded out, but a younger set of jeans guys—ironic jeans guys—has since emerged in the fitness culture. Take the influencer-marathoner Truett Hanes: His brand is built on running very fast and very far … in jeans. He claims that this started as a goof, but it has turned into a business. He now represents a denim company, as well as a chafing cream. The idea of working out in jeans, partly silly and partly serious, is everywhere once you start to look for it. One gymwear brand, Raskol, launched a line of lifter jeggings in 2023 in shades such as “blue steele” and “pale thunder,” with a tongue-in-cheek campaign that had bodybuilders boasting of their pride at using PEDs—that is, “performance-enhancing denims.”

This self-mocking move may be just the prelude to a fuller jeans-guy renaissance, Heffernan suggested. After all, Raskol’s jeggings did sell out, he said. And this wouldn’t be the first time that a traditional signifier of masculinity crept back into mainstream culture by way of performative half jokes. The fashion for bushy beards, and beards’ association with authentic manliness, has followed this same trajectory from irony to earnestness during its various resurgences since the early 19th century. Now the same could be happening to denim workout pants: Today’s goof evolves into tomorrow’s masculine ideal. “I think irony moves into fashion very quickly in fitness,” Heffernan said.

For Kennedy, this process may appear to be going in reverse: His latest workout video shows that he’s in on the joke, that in 2026 he’s capable of pumping irony as well as iron, and that he can engage in what Heffernan described as “a very deliberate deployment of jeans.” But it also shows that there is a recipe, if not a cultural machinery, for rehabilitating out-of-date ideas. Not all of Kennedy’s eccentricities are as quaint as how he dresses in the gym, and there are many ways of going backwards in pursuit of health while pretending that you’ve found a way into the future. MAHA is nostalgia, sometimes with a smirk. The jeans guy dunks himself in water. The jeans guy is reborn.

Olympic skimo is a spectacle. Appearing at the Games for the first time, skimo, short for ski mountaineering, grew from a long tradition of scaling mountains on skis—sometimes for hours on end—for the reward of gliding down, preferably through untracked powder. But at the Olympics, it will involve sprints of approximately three and a half minutes. First, athletes ascend a steep slope on skis outfitted with special fabric strips called “skins,” which prevent them from sliding backwards down the hill. Then they throw their skis on their back and hike in ski boots, put their skis back on for a final ascent, and finally peel off their skins to race downhill.

The events will include a mixed-gender skimo relay—“contrived for the Olympic field,” Sarah Cookler, the head of sport for USA Skimo, the sport’s American governing body, told me. Each team will include one man and one woman, each of whom will run the course twice. Anna Gibson and Cam Smith, both making their Olympic debuts, will represent Team USA.

It’s only fitting that such a new sport should debut on the world stage with a format that’s newly popular. Mixed-gender events, in which each team consists of a set number of men and women, have long had a place at the Olympics: Mixed-pairs figure skating and tennis were each introduced to the Games more than a century ago. But recently, such events have been growing in number as part of a deliberate effort to bring more attention to women’s sports. At Milan Cortina, every major sport category but ice hockey features mixed-gender events.

Women participated in the first Winter Olympics, in Chamonix in 1924, but only in figure skating. Women’s speed-skating exhibitions were included in the 1932 Olympics, but no medals were awarded. In 1936, women competed in alpine skiing, but they weren’t allowed in cross-country until 1952. Since then, the Winter Olympics have slowly been approaching a sort of parity, with women participating in an ever-growing number of events once considered too difficult, dangerous, or scandalous for them.

The International Olympic Committee is advertising the 2026 Games as “the most gender-balanced Olympic Winter Games in history.” That’s based on the fact that women will represent 47 percent of athletes participating and compete in 53 percent of all events; this Olympics is also the first where male and female cross-country skiers are competing at the same distances. But in terms of viewership and publicity, the many mixed-gender events may do more to raise the profile of female athletes than women’s events alone.

Women’s sports, including skimo, tend to attract far fewer spectators than men’s sports do. The mixed-gender relay can help bridge this gap, Smith told me, because in events that feature both men and women, viewers are positioned to watch everyone compete. And if the mixed-gender events allow spectators to get to know more female athletes, that could translate into more people watching the women’s stand-alone events. The IOC is leaning into these events: The Los Angeles Games in 2028 will feature 25 mixed-gender events, including new ones in golf, rowing, and artistic gymnastics.

Gibson told me she’s grown accustomed to elite sport spaces separating men and women as much as possible in the name of equity. She’s also a world-class trail runner and accomplished gravel-bike racer, and in those sports, “the talk has been all about giving women their own start in order to elevate women’s competition rather than having women be buried in the men’s field,” she said. Separate men’s and women’s fields have long been the default in most sports, and for good reason: If women had to compete directly with men, they would rarely have a chance to win. But bringing women and men together in competitions that include both gives women their own space and attention while including all the sport’s athletes within one community. It creates “a lot of camaraderie,” Gibson said, and in her experience, adds to the excitement among spectators.

Women, of course, face many obstacles in sport that cannot be solved by the addition of a few mixed-gender Olympic events. Across sports, male athletes are generally paid more than their female counterparts. In skimo, prize money is equal at the sport’s World Cup, but some other races still have unequal payouts, Cookler said. (Gibson said she avoids those.) Women athletes are still sometimes subjected to sexual harassment and abuse, even on the Olympic level. The Winter Olympics still include one event in which women are not allowed to compete at all—Nordic combined, which consists of ski jumping and cross-country skiing. (The IOC is already considering dropping Nordic combined altogether because of low participation and spectator interest; an IOC spokesperson told me the event “will undergo a full evaluation” following this year’s Olympics, and reiterated the committee’s commitment to gender equality.)

And mixed-gender formats can still be subject to unequal dynamics. Biathlon, a Winter Olympics event that combines cross-country skiing and target shooting, has used the mixed-gender relay format since the 2014 Olympics in Sochi. (Biathlon and luge were the first sports to introduce a mixed-gender format to the Winter Games since figure skating and ice dancing in the 20th century.) But “women always went first in our mixed-gender relays, and people felt it was unfair that a woman could never be the anchor,” Joanne Reid, a three-time Olympian who competed for Team USA last week, told me. In 2019, the sport’s governing body restructured the order of the competition so that the gender of the anchor rotates.

Even as mixed-gender events become more common, skimo’s inclusion in future Olympics is not assured. It’s in the 2026 Olympics because the organizers of this year’s Games proposed it; to continue competing, skimo athletes will need organizers at the next venues to propose its inclusion too. Skimo enthusiasts expect this to happen and hope future Olympics will include events that are longer and more representative of the sport’s origins. “Nobody got into skimo to do the sprint relay,” Smith said. But as he began training for the event, he enjoyed it more than he expected. “It’s really fun because we are accountable to each other,” he said. “I’m racing all out because I know that she’s doing the same for me.”

Back when he was 17 and in high school, Eric Sid fainted. In the emergency room, he was diagnosed with anemia, which can cause fainting spells, and for years he thought that was the end of the story. About a decade later, in the early 2010s, he came down with pneumonia and had blood work done. He took a peek at the results and saw markers of anemia, as he expected. But the report also mentioned that his red blood cells were smaller than normal.

Sid was in medical school at the time, and he immediately thought of a few genetic conditions that could explain this result. One was thalassemia, which causes low levels of hemoglobin, leading to anemia and other related problems. A laboratory test showed that he had this inherited illness. And this meant that he had a gene mutation. Finally, he thought, he had an explanation for symptoms he had been experiencing for years.

Except there was a catch. In the most common forms of thalassemia, people who show symptoms have mutations in both copies of the related genes. Those born with the most severe forms of thalassemia require transfusions for life to get enough healthy red blood cells, and if the condition is not diagnosed soon enough it can be fatal in early childhood. But Sid’s lab results suggested that only one copy was affected, so he was considered a carrier of the illness, who could pass it on to his children but didn’t have it himself. According to conventional wisdom at the time, carriers were asymptomatic, and compared with someone suffering from the disease’s worst manifestations, he seemed fine.  

Sid now works on a rare-disease program within the National Institutes of Health. Since he first found out that he was a carrier for thalassemia, he told me, research has shown that people like him can experience health consequences. These include lethargy and fainting—symptoms that hardly capture the disease’s classic presentation but still have real consequences. And thalassemia is not unique. There are hundreds upon hundreds of known disorders for which carriers were thought to be safe; for a growing number of those diseases, doctors and scientists now believe that being a carrier can come with health problems. Plenty of patients have guessed all along that being a carrier could explain mysteries about their health, Sid said. “It took a while for the science to basically catch up to that suspicion.”

In these types of “recessive” conditions, the people who show the classical manifestation of the disease have a pair of mutated genes. Our 23 chromosomes come in pairs that are essentially near duplicates of each other (with the exception of XY pairs). A person with just one nonworking version of a gene was supposed to be protected by the functioning second copy on the matching chromosome, which would provide cover against any disease. Inheriting two mutated copies of a gene is statistically rare, so many families with carriers may not include members with the full-blown version of a disease. As a result, the mutation can be unknowingly passed down from generation to generation, without carriers being aware of the real consequences.

In October, researchers in Louisiana reported on a case involving a college football player who had heart palpitations during practice. The athlete was a carrier for the blood disorder sickle-cell disease—one of the most common genetic disorders in America. Up to 10 percent of Black Americans are carriers for sickle cell. As far back as the 1970s, scientists noted blood and heart complications in carriers following physical exercise, and a lawsuit following the sudden death of a college football player two decades ago led to widespread screening for the sickle-cell trait in university athletics. However, experts are still trying to understand the risks to carriers.

The Louisiana man survived, but researchers noted that he had a dangerously irregular heartbeat during training and would need cardiac surgery. The authors of the October paper stress that coaches and players need more education about the possible hazards for carriers of the sick-cell trait.

Experts who study cystic fibrosis, which is caused by mutations in the CFTR gene, also want more attention on the health complications that carriers can experience. As many as one in 25 Americans of European descent is a carrier for cystic fibrosis, but many are not aware of their status. For this disease, reports of symptoms in carriers go back at least several decades. Take, for example, infertility. Almost all men who have two mutated copies of the CFTR gene lack vas deferens, and without these tubes, sperm have no path out of the testes. In the mid-’90s, scientists found a handful of cystic-fibrosis carriers who lacked vas deferens, despite only one of their CFTR copies being mutated.

Carriers of cystic fibrosis can face other real health issues—dramatic sinus problems requiring multiple surgeries, pancreatitis, and possibly pancreatic cancer, which researchers have documented in papers over the past several years. “We’ve always said being a carrier of a single cystic-fibrosis mutation doesn’t usually lead to health issues. And usually it doesn’t,” Michael Boyle, the president and CEO of the Cystic Fibrosis Foundation, told me. “However, we do know, and probably have a greater appreciation than ever, that being a carrier can lead to health issues for some.” There are about 10 million cystic-fibrosis carriers in the United States alone, so if even a fraction of them have some degree of symptoms, that amounts to many people with manifestations of the disease.

Questions about carriers’ health problems go beyond well-known diseases such as sickle cell and cystic fibrosis. Consider xeroderma pigmentosum: People with two mutated gene copies are up to 2,000 times more likely to develop melanoma than the average person; a 2023 analysis found strong evidence that some carriers of the disease were also more likely to develop skin cancer. Up to 3 percent of carriers of hereditary hemochromatosis show symptoms such as iron overload in their organs. Carriers of Gaucher disease Type 1 are at increased risk of Parkinson’s. Carriers of LIG4 syndrome experience a version of the immunodeficiency that, in the fully expressed syndrome, causes life-threatening illness.

For many of these diseases, having two mutated copies of the related gene generally means that the disease will come for you. Having one copy can still mean nothing: Plenty of carriers of recessive genetic diseases seem none the worse for it. An estimated one in 20 people is, like Sid, a carrier for thalassemia, but not all people with a copy of the mutation experience anemia and fainting like he did. Why some carriers of genetic illnesses might be affected and others remain free from symptoms is not clear. But “people who are thought to be just carriers but show some symptoms of that disease may sometimes have a second hard-to-discover mutation,” Edward Neilan, the chief medical and scientific officer of the National Organization for Rare Disorders, told me. “They may actually have two mutations.”

Being a carrier can have benefits. One theory of why genetic diseases spread widely is that having one copy of a mutated gene has some advantage. It’s well understood, for example, that being a carrier for sickle-cell disease offers some protection against malaria. And some have theorized that being a carrier for cystic fibrosis can defend against severe cholera, although the evidence for this theory is more scant. A 2023 analysis discovered that although two variant copies of the SCN5A gene elevates a person’s risk of severe heart-rhythm problems, just one copy actually might lower a person’s risk of heart-rhythm irregularities compared with the general population.

Even when being a carrier of a particular disease isn’t itself beneficial, knowing that you are a carrier can be. Carriers of certain variants of xeroderma pigmentosum, for example, might want to go to extra lengths to avoid excessive sun exposure; some carriers of Alpha-1 antitrypsin deficiency, who appear to have a heightened risk of lung issues, might decide not to smoke. And people with the sickle-cell trait might be well-advised to acclimatize before doing sports at high altitudes.

Knowing you’re a carrier for cystic fibrosis might help guide your family-planning decisions, for instance. (Even without vas deferens, a person could still become a father using sperm extraction and in vitro fertilization—which some carriers of cystic fibrosis opt for anyway, to avoid passing on the disease.) But there are limits: The science is still out on whether Trikafta, a relatively new medication that has transformed the disease for many people, would help with sinus or pancreatic issues in carriers. The medication isn’t approved for carriers, either.   

For Sid, knowing that he had a thalassemia mutation—which can cause dizziness—has made him feel less bad about his difficulty with intensive physical training, for example. And he is comforted to know what likely caused his high-school fainting episode. Finding out about the mutation in his genome gave him a fuller picture of his health. “Personally,” he said, “that’s kind of how I saw it—this kind of gave me some more understanding.”

In 2021, just months after the first COVID vaccines debuted, concern was growing about an exceedingly rare but sometimes deadly outcome of certain shots. Two related vaccines—one from AstraZeneca and the other from Johnson & Johnson—were linked to dangerous blood clotting.

Out of almost 19 million doses of Johnson & Johnson’s version given in the United States during the first two years of the pandemic, at least 60 such cases were identified. Nine of them were fatal. In the United Kingdom, where almost 50 million doses of the AstraZeneca shot were given, 455 cases occurred; 81 people died. In Germany, at least 71 cases were identified, also linked to AstraZeneca. By late spring, use of both the AstraZeneca and the Johnson & Johnson vaccine was paused, and ultimately both were pulled from the market. But the mystery surrounding the rare blood clotting caused by these vaccines lingered.

Now researchers believe they have cracked the case. They have hard evidence for how the blood clotting happened, and they believe that their findings could help make similar vaccines even safer. Understanding the blood-clotting problem is important, they say, because vaccines of this type could be essential in protecting people during future pandemics.

The team that initially gave this condition a name—vaccine-induced immune thrombotic thrombocytopenia, or VITT—included Andreas Greinacher, a blood expert at the University of Greifswald, in Germany. Back in 2021, as the cases of VITT emerged, he and others were unsure of what precipitated them. One theory was that they were caused by the body’s accidental reaction to the type of virus used in both the AstraZeneca and Johnson & Johnson vaccines: adenoviruses, which had been engineered to prompt the body to recognize the pandemic coronavirus but were unable to replicate and considered harmless to people. Scientists had noticed that patients with VITT had telltale markers in their blood—antibodies that bind to a chemical signal released by platelets. Maybe a reaction to the adenovirus was causing immune cells to mistakenly go after a blood component and precipitate clotting. An alternative theory was that the body was reacting to a portion of the coronavirus called “spike protein,” which showed up as part of the immunization.

In a study published today in The New England Journal of Medicine, Greinacher and his colleagues show that the first theory was correct: VITT was a response to the adenovirus gone awry. And they discovered a further twist: This immune overreaction happened in people who were genetically prone to it.

In the study, Greinacher and his colleagues looked at the antibodies in stored blood from 21 patients with VITT. Among those antibodies, they found a subset that could glom on to a portion of the adenovirus and to one of the body’s own molecules, PF4, that can influence blood clotting. A person who received one of the adenovirus vaccines but did not have a reaction also had antibodies against that same part of the adenovirus. But, crucially, that person’s antibodies did not cross-react with PF4.

Those antibody molecules also offered clues about the immune cells that made them. And the scientists were able to link the immune cells responsible for VITT to patients who had two specific DNA variants. A wider survey of 100 VITT patients found that all of them had immune cells with one of these genetic types—which are far from universal. This signaled to the researchers that having these particular variants is a strong risk factor for blood clotting following an adenovirus vaccine.

But the study also showed that this genetic background on its own was not enough to cause VITT. The immune cells that made the dangerous antibodies had experienced an additional small genetic change, and that extra mutation had prompted them to produce those cross-reactive molecules.

In the past, scientists have suggested that genetic predispositions might explain some adverse events that happen after vaccination. For example, some data have indicated that certain people were genetically prone to developing narcolepsy following a version of swine-flu vaccine that was briefly used in Europe. But the new study from Greinacher and his team is the first to provide concrete evidence of how people with a particular DNA variant can develop self-sabotaging antibodies following a vaccination. Arnold Lining Ju, a biomedical engineer at the University of Sydney who has studied blood clotting, told me that the paper was a landmark finding in part because of how elegantly it explains the way a specific genetic trait, combined with a particular chance mutation in certain cells, creates VITT. And because the study shows that multiple genetic changes are involved, it finally explains why this immune reaction is so rare, he said.

This discovery will help guide researchers more than it will influence vaccination choices for individual patients. Most vaccine recipients will not know their genetic predisposition to an adverse event, Jennifer Juno, a vaccine researcher at the University of Melbourne, points out. But this type of work will help improve vaccine design—particularly in the field of “precision vaccinology,” in which vaccines are tailored to individual traits, Joanne Reed, the director of the Centre for Immunology and Allergy Research at the Westmead Institute in Australia, told me.

These results also mean that adenovirus-based vaccines could be made safer if they can be designed without the protein region that triggered the dangerous antibodies in VITT. “Instead of abandoning an entire vaccine platform because of a rare problem, we can engineer around the specific issue, and that’s the power of this kind of science,” Joann Arce of the Precision Vaccines Program at Boston Children’s Hospital told me. The hope is that understanding the biology of a rare event like VITT, and then addressing it, helps bolster public trust in vaccines too. Greinacher told me that adenovirus-based vaccines remain vital, including for the development of vaccines for diseases that affect mostly low- and middle-income countries. The shots could also be useful in a future pandemic, because they can be scaled up in production relatively quickly.

Still, this one study may not have entirely answered the question of why adenovirus-based COVID vaccines caused clotting. A study published last year from Ju’s group suggested that a separate biophysical mechanism might cause a viral component found in the AstraZeneca vaccine to directly aggregate platelets, independent of the immune reaction identified in VITT. And a bigger mystery remains open too—why infections themselves are sometimes associated with dangerous blood clotting. Rushad Pavri, an immunologist at King’s College London, told me that the new study—because it shows how similarities between a virus particle and an innate protein involved in clotting can confuse the immune system—can shed light on that question. Ultimately, understanding why viruses can provoke immune overreactions might help limit damaging complications from sickness to begin with.

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In the winter of 168 C.E., the famed Greek physician Galen arrived in Aquileia, an Italian city on the northern edge of the Adriatic. The city had grown large since its founding as a Roman colony, but during the 200-year Pax Romana, its fortifications had been allowed to deteriorate. After an armed group of migrating Germanic peoples had crossed the Danube a year earlier, the Roman co-emperors, Marcus Aurelius and Lucius Verus, had rushed to the city, raising two legions and rebuilding its defenses; they planned to use it as a base of operations against the invaders.

Galen had been summoned, however, to help fight a different kind of invader. A plague, likely an early variant of smallpox, had traveled to Aquileia with the troops, and held the city in its grip. The emperors fled, but Verus succumbed to the disease on the road to Rome. Galen tried to slow the wave of illness, but most of the people in Aquileia perished.

This article was featured in the One Story to Read Today newsletter. Sign up for it here.

In the winter of 168 C.E., the famed Greek physician Galen arrived in Aquileia, an Italian city on the northern edge of the Adriatic. The city had grown large since its founding as a Roman colony, but during the 200-year Pax Romana, its fortifications had been allowed to deteriorate. After an armed group of migrating Germanic peoples had crossed the Danube a year earlier, the Roman co-emperors, Marcus Aurelius and Lucius Verus, had rushed to the city, raising two legions and rebuilding its defenses; they planned to use it as a base of operations against the invaders.

Galen had been summoned, however, to help fight a different kind of invader. A plague, likely an early variant of smallpox, had traveled to Aquileia with the troops, and held the city in its grip. The emperors fled, but Verus succumbed to the disease on the road to Rome. Galen tried to slow the wave of illness, but most of the people in Aquileia perished.

Americans watching the Super Bowl today will hear a tantalizing pitch: You, too, can live like the rich. All you need is a way to order up health care the way they do.

A new ad scheduled to air during the big game, from the telehealth company Hims & Hers, opens with the provocation “Rich people live longer.” A dizzying montage spoofing America’s wealthiest and most wellness-obsessed characters follows: An ageless man bathes in red light in the manner of Bryan Johnson, the multimillionaire who rose to fame for his fanatical efforts to live forever. A bald man doffs a cowboy hat as a rocket blasts off—clearly an allusion to Jeff Bezos, who in recent years has become incredibly buff and backed a buzzy age-reversal start-up. Surgeons pull the sagging face of a woman taut as a drum, perhaps a reference to the Kardashian matriarch Kris Jenner’s notorious 2025 facelift. Dan Kenger, the chief design officer at Hims & Hers, told me in an email that the actors in the commercial represent only “symbols of an intimidating, members-only healthcare culture.” But the parallels to real life are too obvious to ignore. “They get the best of everything,” the voiceover continues. “So why don’t you?”

Hims & Hers is best known for offering weight-loss and hair-restoration treatments, but the ad positions the company as a gateway to a different world of health care—one with concierge doctors who are available on demand to offer personalized, cutting-edge therapies. “America’s healthcare is a tale of two systems: one elite, proactive tier for the wealthy, and a broken, reactive one for everyone else,” Kenger said. Hims & Hers’ actual offerings, which include diagnostic blood testing and hormone therapy, may be more mundane than a facelift, but the ad emphasizes one thing they all share: They’re all available to you, for a price.

Telehealth platforms such as Hims & Hers offer patients the ability to pay out of pocket to quickly seek treatment for their ailments. Generally, they assert that patients must consult virtually with a medical provider before receiving a prescription, but this requirement isn’t featured prominently in most ads. The new spot from Hims & Hers notes that its doctors are around to chat, and—in the fine print—mentions that a consultation with a provider is required before receiving treatment. But unless you’re squinting at the screen, the message that comes across is that health care is primarily a transaction between patient and company.

In general, telehealth platforms have come to essentially function as a kind of Amazon for drugs, making it easier for people to get prescriptions for controlled substances such as Adderall and testosterone. The companies sidestep the high cost associated with many name-brand drugs by using compounding pharmacies to offer cheaper, nearly identical versions of the medications. In theory, a licensed provider writes the prescription after a thorough medical assessment. But in just the past two years, two different telehealth practices have been sanctioned for inappropriately prescribing stimulants. (Hims & Hers has not faced any federal investigations for its prescribing practices.)

Last year, Hims & Hers ran a Super Bowl ad similarly focused on democratizing care—specifically GLP-1s for weight loss. It asserted that America’s obesity epidemic is caused by “the system,” which keeps people sick by making health care unaffordable. When name-brand GLP-1s such as Wegovy first started being prescribed for weight loss, in 2021, they were inaccessible for most Americans because of their steep cost and insurance providers’ limited coverage. Rumors that celebrities were using the drugs for cosmetic reasons sparked a mix of outrage and envy, and as Americans of more humble means began to see the results the drugs could bring about, many began scrambling for cheaper sources—a perfect opportunity for Hims & Hers and its peers.

[Read: What is Hims actually selling?]

But Americans aren’t clamoring for just GLP-1s anymore. Medications such as testosterone and peptides—a largely untested class of drugs with a wide range of purported health benefits—are in high demand too. Like GLP-1s, they have been touted by wealthy, high-profile figures, including Gwyneth Paltrow, Joe Rogan, and Health Secretary Robert F. Kennedy Jr. Hims & Hers has positioned itself to meet these demands. Last year, the company launched its low-testosterone treatment program and bought a peptide-manufacturing facility. It plans to use that factory to make its own “personalized” drugs.

Such language evokes the concierge treatments enjoyed by the rich. But in telehealth-platform parlance, personalization usually refers to creating a version of a name-brand medication that fits a patient’s needs by, say, changing the dose, adding other active ingredients, or offering it in a different format. These compounded versions aren’t reviewed by the FDA—in fact, the FDA announced Friday that it had asked the Justice Department, out of concern for consumer safety, to investigate Hims & Hers for selling compounded GLP-1 pills. The move is part of the DOJ’s wider plan to take “decisive steps” to restrict the marketing of compounded GLP-1s.

The medical community is concerned that telehealth platforms too easily allow patients to take unsafe drugs—or drugs they simply don’t need. The Obesity Society, a scientific organization, warns people not to use compounded GLP-1s, because they may not contain the appropriate active ingredients. (As I wrote recently, men’s-health experts are also worried about the cardiovascular and reproductive consequences of unnecessary testosterone-replacement therapy.) When I asked Hims & Hers about the DOJ investigation, a spokesperson directed me to a public statement posted yesterday on X, in which the company said it would stop selling compounded GLP-1 pills. “We remain committed to the millions of Americans who depend on us for access to safe, affordable, and personalized care,” the statement said.

[Read: T-maxxing has gone too far]

The Hims & Hers ad is shrewd in its heavy-handedness. It validates Americans’ frustration with health care and positions itself as a deliverer of justice. (The ad is narrated by the rapper Common, known for his socially conscious music; in its Super Bowl ad last year, the company used Childish Gambino’s “This Is America,” a song about systemic racism and gun violence, to pile onto its message of a broken system.) Pew Research Center data released a few days ago show that 71 percent of Americans are worried about the cost of health care.

At the same time, Americans can’t seem to stop imitating billionaires’ wellness habits: untested peptides, NAD+ IV drips, Erewhon smoothies, red-light masks, keto diets. A slew of other planned Super Bowl ads promoting new visions of health illustrates just how central the pursuit of wellness has become to American life and the American economy, even when the benefits of so many of these practices are questionable at best. Hims & Hers is accurate in its diagnosis that much of this country’s gap in health and longevity boil down to wealth. But the treatment it prescribes seems to be an unlikely cure.

Nothing about TrumpRx is subtle. When you open up the government’s new online drugstore, the first thing you see is a banner with giant text: “Find the world’s lowest prices on prescription drugs.” Launched last night, TrumpRx allows Americans to purchase certain medications at steep discounts—either by buying them directly from the drug company or by showing a coupon at the pharmacy. “Thanks to President Trump, the days of Big Pharma price-gouging are over,” the website says.

TrumpRx does make a compelling case that the president has mounted an extraordinary effort to stop pharmaceutical companies from ripping off Americans. The website offers discounts on some 40 drugs—the result of months of negotiations between drugmakers and the Trump administration. In a press conference announcing TrumpRx yesterday, Trump boasted that “16 of the 17 largest pharmaceutical companies have signed agreements” to list their drugs on the website. “And the other one is coming,” he added. The Trump administration was able to negotiate a nearly 85 percent discount on a trio of drugs typically used as part of IVF. Americans can also buy Wegovy, the wildly popular weight-loss injection, for as little as $199 a month, a fraction of the original list price.

But these are the exceptions. Most Americans looking for their prescription drugs won’t find that many deals on the site. Health care is complicated already, and TrumpRx apparently does not always offer the cheapest or best option. Those with insurance—some 85 percent of Americans—typically will get a better deal using the coverage they already have than they would paying out of pocket on TrumpRx. More than three-quarters of Americans with commercial insurance are eligible to pay $20 or less for a month’s supply of Xeljanz, a rheumatoid-arthritis drug. But customers paying cash via TrumpRx will still shell out more than $1,500.

[Read: Trump’s Ozempic deal has a major flaw]

Even people without insurance may be able to find better prices in some cases. Consider Protonix, a drug from Pfizer used to treat acid reflux. TrumpRx offers the drug for just over $200—a 55 percent discount from its typical $447. But what the website does not explain is that there’s a much cheaper, generic version of Protonix on the market (but not available through TrumpRx). According to GoodRx, a drug-discount website similar to TrumpRx, the generic version can be purchased for less than $10. The same is true for Pristiq, an antidepressant. Consumers can buy the drug for $200 on TrumpRx or get the generic via GoodRx for a tenth of the price. Patients going through financial hardships can also sometimes qualify for charity programs, which subsidize their prescriptions.

The big winners of yesterday’s announcement seem to be not patients, but drug companies. The Trump administration got drugmakers to the negotiating table last year by writing letters to the companies threatening to “deploy every tool in our arsenal to protect American families from continued abusive drug pricing practices.” Drugmakers were able to turn the threat into a PR opportunity: When Pfizer cut a deal to participate in the program, the company’s CEO, Albert Bourla, was brought to the West Wing, where Trump called the drug company “one of the greatest in the world.”

Drug companies have also successfully protected their ability to charge whatever they please for some of their biggest moneymakers. Yesterday, Trump claimed that the website includes discounts for “dozens of the most commonly used prescription drugs,” but many of the pharmaceutical industry’s best-selling products—some of which also are among their more expensive offerings—are absent from the website. Take Keytruda, Merck’s cancer drug that was the world’s best seller until it was recently surpassed by the weight-loss and diabetes injection tirzepatide: That drug retails for roughly $12,000 for a three-week course of treatment, and it is missing from TrumpRx. Of the top 10 best-selling prescription drugs in 2024, only one—Ozempic—is listed on TrumpRx.

TrumpRx may become better with age. A White House press release from December named multiple additional drugs that are supposed to be included in TrumpRx but are not. The drugmaker Gilead Sciences, the White House touted in the press release, will sell one of its hepatitis-C medications for about $2,400 rather than its original asking price of nearly $25,000. Kush Desai, a White House spokesperson, told me in an email that only five companies’ drugs have been added to the TrumpRx website so far. In its negotiations, the administration has also secured commitments from drugmakers that when they launch new drugs, they will not charge Americans more than they charge individuals in similar nations, which has the potential to dramatically lower the prices Americans pay for new medicines. (It’s still unclear, however, if all of those new drugs will also be available on TrumpRx.)

For Americans who find discounts on TrumpRx, the platform is likely to make a meaningful difference in their lives. It’s addressing, in its so-far-limited ways, a persistent problem in American life. That said, Trump has claimed before to have provided Americans with real relief at the pharmacy counter. During his first term, the president said that seniors would soon receive $200 discount cards in the mail that they could bring to the pharmacy to help defray the high costs of their drugs. The cards never showed up. This time, the downloadable coupons, at least, are real. They are branded with a golden eagle holding a TrumpRx ribbon in its talons.

Since measles vaccination became common among Americans, the logic of outbreaks has been simple: When vaccination rates fall, infections rapidly rise; when vaccination rates increase, cases abate. The United States is currently living out the first half of that maxim.

Measles-vaccination rates have been steadily declining for several years; since last January, the country has logged its two largest measles epidemics in more than three decades. The second of those, still ballooning in South Carolina, is over 875 cases and counting. In April, measles may be declared endemic in the U.S. again, 26 years after elimination.

When and if the maxim’s second part—a rebound in vaccination—might manifest “is the key question,” Paul Offit, a pediatrician and vaccine expert at Children’s Hospital of Philadelphia, told me. Experts anticipate a shift eventually. Vaccine coverage has often been beholden to a kind of homeostatic pull, in which it dips and then ricochets in response to death and suffering. In 2022, for instance, in the weeks after polio paralyzed an unvaccinated man in Rockland County, New York, the families of more than 1,000 under-vaccinated children heeded advice to immunize.

During past outbreaks, though, health authorities at local, state, and federal levels have given that same advice—vaccinate, now—loudly, clearly, and persistently. In 2026, the U.S. is facing the possibility of more and bigger measles outbreaks, as federal leaders have actively shrunk vaccine access, dismissed vaccine experts, and sowed doubts about vaccine benefits. Under these conditions, many experts are doubtful that facing down more disease, even its worst consequences, will convince enough Americans that more protection is necessary.

After the first major rash of measles cases appeared in and around West Texas about this time last year, many local families did rush to get vaccines, including early doses for infants; some families living near South Carolina’s outbreak, now bigger than West Texas’s was, have opted into free vaccination clinics too. Even in states far from these epidemics, such as Wisconsin, health-care providers have seen an uptick in vaccination, Jonathan Temte, a family-medicine physician and vaccine-policy expert at the University of Wisconsin at Madison, told me. But, he said, those boosts in interest have been concentrated primarily among people already enthusiastic about vaccination, who were seeking additional protection as the national situation worsened. At the same time, many of South Carolina’s free vaccination clinics have been poorly attended; some community members hit by the worst of the outbreak in West Texas have stood by their decision to not vaccinate.

Protection against measles has always been fragile: Sky-high levels of vaccination—at rates of at least 92 to 95 percent—are necessary to stave off outbreaks. And after holding steady for years, uptake of the measles-mumps-rubella (MMR) vaccine has been dropping unevenly in communities scattered across the U.S. since around the start of the coronavirus pandemic, pulling down the nationwide average. Recent research from a team led by Eric Geng Zhou, a health economist at the Icahn School of Medicine at Mount Sinai, has found that, although many communities in the Northeast and Midwest have generally high MMR-vaccine uptake, others in regions such as West Texas, southern New Mexico, and the rural Southeast, as well as parts of Mississippi, don’t have much protection to speak of.

COVID can bear some of the blame for these patches of slipping vaccination. It disrupted families’ routine of visits to the pediatrician, leading to delayed or missed vaccinations. Those interruptions quickly resolved for some families, Zhou told me, but they remained for many others, lagging, for instance, among people of lower socioeconomic status who are less likely to have consistent access to health care and reliable health information. At the same time, the pandemic deepened political divides over public-health policies, including vaccination. In the years since, Republicans have become substantially more hesitant than Democrats about immunizing their children. “The COVID pandemic created this persistent divergence,” Zhou told me.

Pockets with under-vaccinated people have always existed, tracking alongside groups that are less likely to engage with all kinds of medical care, including people with less education or lower income, or those who belong to certain ethnic minorities. Anti-vaccine activists—including Robert F. Kennedy Jr., now the secretary of the Department of Health and Human Services—have also spent years spreading misinformation about the vaccine. But maybe most crucial, vaccination status clusters in communities—depending intimately on whether, for instance, children are raised by parents who are themselves vaccinated. The net effect of COVID, misinformation, and changing political tides is that the chasms between the vaccinated and unvaccinated have widened, an especially dangerous proposition for measles, a virus that is estimated to infect 90 percent of the unimmunized people it encounters.

Last year, as measles ignited in West Texas, some experts wondered whether attitudes about the MMR vaccine might shift once the virus killed someone. Since the start of 2025, three unvaccinated people have died from measles, two of them young children. But because that outbreak centered on several rural Mennonite communities that have long been distrustful of vaccines, many Americans seem to have treated those three deaths as a mostly isolated problem, Noel Brewer, a vaccine-behavior expert at the University of North Carolina Gillings School of Global Public Health, told me. (Brewer was a member of the CDC’s Advisory Committee on Immunization Practices before Kennedy overhauled the group entirely last year.)

More broadly, the disease still has a misleading reputation as harmless enough that “it’s not a big deal if you get it,” Rupali Limaye, a vaccine-behavior expert at Johns Hopkins University, told me. But even if measles’ severe outcomes were more common, Limaye and others were doubtful that many more Americans would be moved to act. COVID vaccines still offer protection against the disease’s worst outcomes, yet so far this winter, just 17 percent of adults and 8 percent of children have gotten a COVID shot. And although the seasonal flu typically hospitalizes hundreds of thousands of people in the U.S. each year, tens of thousands of whom die, flu-vaccine uptake regularly hovers below 50 percent. For measles, “how many deaths is enough to be a tipping point?” Offit asked. “I don’t know that.”

If anything, the nation’s top health officials have encouraged people to embrace the tolls of infectious illness. The Trump administration responded to the deaths last year with relatively tepid messages about the benefits of measles vaccines—which are excellent at preventing severe illness, infection, and transmission—all while promoting nutritional supplementation with vitamin A. More recently, CDC’s new principal deputy director, Ralph Abraham, described the prospect of measles becoming endemic in the U.S. as “just the cost of doing business.” Last month, CDC ended long-standing recommendations urging all Americans to receive an annual flu shot; later that week, Kennedy told CBS News that it may be a “better thing” if fewer kids get vaccinated against the flu. And Kirk Milhoan, the new chair of CDC’s vaccine advisory committee, recently questioned the need for the MMR vaccine, arguing that measles’ risks may now be lower than they once were, in part because hospitals are better equipped to treat the disease than they used to be.

When reached for comment over email, Andrew G. Nixon, the deputy assistant secretary for media relations at HHS, disputed the notion that the department has hindered the country’s response to measles, writing, “Under Secretary Kennedy, CDC surged resources and multiple states declared measles outbreaks over in 2025.” He added that “Secretary Kennedy and other leaders at HHS have consistently said that vaccination is the best way to prevent the spread of measles.”

The counsel of health-care providers, not federal health officials, remains a top predictor of whether people will immunize. But when vaccine uptake has wavered in the past, governments have been key to buoying those levels again. In the 1970s, for example, after safety concerns about a whooping-cough vaccine—later proved false—caused rates of uptake to plummet in the United Kingdom and spurred a series of major outbreaks, an eventual government-sponsored campaign helped limit the dip in vaccination to a few years. In the 2010s, rising rates of families seeking nonmedical exemptions for vaccination in California helped precipitate the state’s Disneyland measles outbreak, which spread to six other states, as well as Canada and Mexico; MMR-vaccination rates throughout California jumped above 95 percent only after new state legislation strengthened school mandates. And in the early 1990s, local health officials ended a Philadelphia measles epidemic—which by then had sickened at least 1,400 people and killed nine children—after they took the extreme step of getting a court order to compel community members to vaccinate children.

When governments withdraw support for vaccines, immunization rates can crater. In 2013, an unfounded safety concern about the HPV vaccine prompted Japanese health authorities to suspend strong national recommendations for the immunization; the move caused uptake among adolescent and young teenage girls to drop, from about 70 to 80 percent to less than 1 percent within a year, according to Brewer, who is co-authoring a research paper on the subject. Japan did not reinstate its HPV recommendation until nearly a decade later—and coverage has since recovered to only about half of its original baseline.

Nixon, the HHS spokesperson, wrote that the U.S. is now following the approach of peer nations that “achieve high vaccination rates without mandates by relying on trust, education, and strong doctor-patient relationships.” But Kennedy has also publicly discouraged people from “trusting the experts.” Limaye, who consults with local health-care providers, said that the biggest question that her contacts are now hearing from patient families is “Who am I supposed to believe?” Meanwhile, CDC’s website now contradicts the widespread and decades-long scientific consensus that vaccines don’t cause autism.

If MMR-vaccine uptake does rebound, experts suspect it will rise unevenly across the country, likely skirting the politically red regions where vaccination rates most urgently need to increase. In this way, the self-reinforcing nature of vaccination status is dangerous: Even while highly protected groups might double down on immunization, under-vaccinated groups can remain unprotected. Leaving enough places lingering below the crucial measles-vaccination threshold “will ensure repeated and large outbreaks,” Brewer said. West Texas and South Carolina were just the start; this year, measles will sicken more people, which means more deaths will follow, and likely soon. The Trump administration is testing how much resilience American vaccination rates have in the absence of federal support, and the answer emerging for measles so far is: not enough.