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—plummeted rates of uptake 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.