With three measles cases in three different Wisconsin communities since New Year’s Day, the state could be vulnerable to a larger outbreak, according to public health experts.

“We’ve gotten three cases in the state of Wisconsin so far in 2026, and there’s been many years in which we had zero,” said Dr. Joe McBride, a pediatric infectious disease physician at UW Health Kids and assistant professor of medicine at the University of Wisconsin School of Medicine and Public Health. If the cases spread, “those are incredibly, incredibly difficult for us to slow down and to prevent.”

“There may be only three people with measles, but the cases are occurring in three different places,” said Ajay Sethi, director of the Master of Public Health Program at the UW medical school. “These are three separate public health responses, and that is significant given the potential for spread to others from just one person with measles.”

In January, state health officials reported a measles infection in a Waukesha resident. This month, measles infections have been identified in Dane County and in a person who traveled through Milwaukee County’s Mitchell International Airport to Walworth County. The Wisconsin Department of Health Services has also identified possible locations when other people might have been exposed in the Dane County and Mitchell Airport cases. All three were described as connected to travel. 

“It’s good, in that they don’t seem to be related, and we don’t see an outbreak,” McBride said. “But it’s also bad because that means there’s a lot of measles,” he added. “It’s kind of a tinderbox, and we have large cohorts of our population who are not immune.”

The year 2025 saw a resurgence of measles nationwide, approaching 2,000 cases, Stateline reported in December, with outbreaks in Texas, Arizona, South Carolina, Utah and New Mexico.

Sethi said an August 2025 cluster of cases in Oconto County started with a case in St. Croix County in someone who was visiting from out of state. Across Wisconsin in 2025, “Ultimately 36 people got measles, and two of them needed hospitalization,” he said.

‘Incredibly infectious’ illness

Although most widely known for its trademark rash, the measles virus “is a respiratory virus, just like really any other cough and cold virus that we think about,” said McBride. “However, it’s incredibly, incredibly infectious.”

The virus is airborne, McBride said, and can hang in the air for up to two hours. In one landmark case, at the 1991 Special Olympics at the Minneapolis Metrodome, a participant on the field had measles, McBride said, “and people who were susceptible to the infection got the infection who were sitting in the upper deck.”

Vaccination is the primary tool to stop measles, and in Wisconsin as well as in much of the U.S. vaccination rates are below the 95% that public health practitioners say allows for widespread “herd immunity.”

The measles vaccine is usually given in combination with mumps and rubella vaccines, first at the age of 1 with a booster by the time a child is 5.  

Some people aren’t eligible for the vaccine, either because they’re younger than 6 months old or because they have a compromised immune system due to another illness.

“It’s a live vaccine, and live vaccines have the potential of causing infections in people who are immune-compromised, like bone marrow transplant recipients or a patient with AIDS” or people on medications that suppress the immune system, McBride said.

That makes it even more important for people who are eligible to get the vaccine, public health experts say.

A national map produced by ABC News in collaboration with Boston Children’s Hospital, Harvard Medical School and Icahn School of Medicine at Mount Sinai in New York shows that none of the counties in Wisconsin has as many as 90% of  5-year-olds fully vaccinated for measles.

The lowest rates of measles vaccinations for that age group are in Portage and Columbia counties, with fewer than 60%. A cluster of counties around Oshkosh have vaccination rates in the low 60s; another cluster around Eau Claire in the mid-60s, and Milwaukee, Racine and Waukesha counties have vaccination rates in the high 60s. In the rest of the state, vaccination rates for children 5 or younger are in the range of 70% to more than 80%.

“The decision to get vaccinated is still very nuanced,” Sethi said — influenced by a variety of factors. Those include complacency, which may lead people to dismiss the need for a vaccine, he said. Other factors include how convenient it may be to get the shot, confidence in the vaccine’s effectiveness and a sense of community responsibility.

HHS shift, CDC silence

One source of shakier confidence has been a shift at the U.S. Department of Health and Human Services and the Center for Disease Control and Prevention (CDC), in the agencies’ stance on vaccines under HHS Secretary Robert F. Kennedy Jr., who had a history of anti-vaccine campaigning for years before his appointment.

Kennedy has made some appeals for people to get the measles vaccine, and in an appearance on CNN Sunday, Dr. Mehmet Oz, director of the Centers for Medicare & Medicaid Services, urged viewers, “Take the vaccine, please.”

But researchers at Johns Hopkins University in a report published in December documented that amid the 2025 measles surge, CDC social media accounts “have gone quiet, creating a ‘void’ in online health communication. In this vacuum, measles messaging has been dominated by news media rather than expert health authorities, resulting in polarized and potentially inaccurate information.” 

By the year 2000, measles vaccination had become so widespread that the U.S. was identified as having eliminated the disease. Canada, which also had that status, lost it in 2025, and the U.S. appears to be on the verge of losing it as well, Sethi said.

Yet the measles vaccine is both extraordinarily effective and essentially the only weapon against the virus.

“There isn’t any kind of other medicine that can abort it,” McBride said. “It is completely dependent on either preventing it or having natural infection and supporting the individual through it.”

The infection itself can be extremely serious, however, he said. In addition to fevers, cough and the rash, which is painful, secondary complications can do much more bodily damage. Those can include bacterial infections, pneumonia, vision and neurological damage and cardiovascular system harm as well.

In about one of every 1,000 cases, a delayed neurological condition can arise 10 years after a person is infected “that is completely fatal,” McBride added. Among the hundreds of cases across the U.S. now, “there certainly is somebody who’s walking around today who will be dead of measles in 10 years, who doesn’t know it. And that’s incredibly scary.”

People born before 1957 are more likely to have natural immunity from having been exposed to measles in childhood. “After 1957 we can’t really make that claim for people,” McBride said. “And so our immunity is dependent on vaccine status.”

People living in Wisconsin can look up their immunization status on the Wisconsin Immunization Registry, McBride said. Some people’s records might be incomplete, either because they received a vaccine in another state or because they got a vaccine before 1999, when the registry was launched. Earlier vaccines were logged on paper by health providers, according to the Wisconsin Department of Health Services.

Interest in the MMR vaccine appears to be rising. News reports and public health announcements drawing attention to recent measles cases and the importance of the vaccine “certainly raises new awareness and attention to it,” he said.

More patients are asking about the shot and more doctors and nurses are asking whether there needs to be any changes to the current vaccine schedules recommended by the American Academy of Pediatrics or the state health department.

McBride said the current cases in Wisconsin don’t point to any change in those recommendations, however. For health care providers, “The most helpful interventions would be to evaluate your patients and make sure they are up to date with the measles vaccine.”

A sign at a University of Utah health clinic warns visitors about the spread of measles. Under the Trump administration, federal health officials have cut back the number of recommended vaccines, and more states are offering exemptions for parents who don't want to vaccinate children entering public schools. (Photo by McKenzie Romero/Utah News Dispatch)

States that were leaders in childhood vaccination before the pandemic are among those losing ground as exemptions and unfounded skepticism take hold, encouraged by the Trump administration’s stance under U.S. Health and Human Services Secretary Robert F. Kennedy Jr.

Expanded exemptions for parents are likely to drop both Mississippi and West Virginia from the top national rankings they held before the pandemic, according to a Stateline analysis of federal data. Other states like Florida, Idaho, Louisiana and Montana also are pushing the envelope on vaccine choice.

At least 33 states were below herd immunity in the 2024-25 school year, compared with 28 states before the pandemic in 2018-2019, the analysis found. Herd immunity refers to the percentage of people who must be vaccinated or otherwise immune from an infectious disease to limit its spread.

Research shows that in the case of measles — a highly contagious disease — states need to maintain at least 95% vaccination rates to protect people who can’t get vaccinated. Other diseases have similar herd immunity rates. People who can’t be vaccinated might include infants too young to receive certain vaccines and those with underlying health conditions.

Misinformation and expressions of distrust from influential leaders have an effect on parents, doctors say, as do new state exemptions making it easier for families to avoid the vaccines.

Some people who never questioned vaccines before notice a national debate and get confused, said Dr. Patricia Tibbs, a pediatrician in rural Mississippi and president of the Mississippi chapter of the American Academy of Pediatrics. New religious exemptions may already be fueling an increase in pertussis, also known as whooping cough, in Mississippi, she said.

“If they hear something about it in the news, then it must be right, they think,” Tibbs said. “We’re just following the guidelines and informing patients that this is a scientific discussion. Nothing has changed about the science. But people who don’t know science are making decisions.”

Under Kennedy’s leadership, federal support for vaccination has continued to slide, and many states have joined a movement to set their own course by following more science-based recommendations from doctors. On Jan. 26 the Governors Public Health Alliance, a group of 15 Democratic governors, endorsed child and adolescent vaccination standards from the American Academy of Pediatrics rather than the federal government.

Federal health officials in Trump’s administration have cut back the number of recommended vaccines. The chair of a vaccine advisory committee, pediatric cardiologist Kirk Milhoan, suggested in a Jan. 22 podcast that individual freedom was more important than protecting community health with vaccines, even for measles and polio.

New leading states

Before the pandemic, Mississippi and West Virginia had the highest kindergarten vaccination rates in the nation, according to the Stateline analysis. About 99% of kindergartners in each state had their required vaccinations before entering public schools in the 2018-2019 school year.

In the latest statistics for the 2024-25 year, Connecticut gained the No. 1 spot, followed by New York and Maine. Those states have reined in exemptions to school vaccine requirements, while Mississippi and West Virginia have begun to allow more exemptions.

West Virginia didn’t report vaccinations to the federal Centers for Disease Control and Prevention for the 2024-25 school year. The state department of health told Stateline the data wouldn’t be available until later this year.

But the state is likely to be pushed out of the top 10. Republican Gov. Patrick Morrisey issued an executive order a year ago giving parents the right to ask for religious exemptions. To date, the state has approved 693 such requests for the current school year, spokesperson Gailyn Markham wrote in an email. That alone is enough to shift the state’s ranking significantly.

Stateline computed an average of required kindergarten vaccination rates to compare states. The analysis uses 2018-19 as a pre-pandemic baseline because a large number of states did not report the information in 2019-20 in the chaos that followed the early COVID-19 spikes and school closings.

A January study published by JAMA Pediatrics found increased vaccination rates among kindergartners in states that had repealed nonmedical exemptions, suggesting the repeals “played a role in maintaining vaccination coverage in repeal states during a period of heightened vaccine hesitancy.”

Requirements and exemptions

All 50 states and the District of Columbia require students to have certain vaccines before attending public school. They also all allow exemptions for children who cannot receive vaccinations for medical reasons, and most states allow nonmedical exemptions, often for religious or sometimes personal reasons. But Florida Republican Gov. Ron DeSantis’ administration has proposed dropping all requirements, and Idaho enacted a 2025 law allowing vaccination exemptions for any reason. Idaho had the lowest rate of kindergarten vaccination, about 80% in the 2024-25 school year before the law took effect in July last year.

Louisiana in 2024 enacted a law dropping COVID-19 vaccine requirements for public schools, and the state has opted to halt publicity about flu vaccination and end public vaccine clinics.

A Florida bill that progressed out of committee in January would maintain school vaccine requirements but expand exemptions to include “conscience” as well as medical and religious reasons.

Dr. Jennifer Takagishi, a Tampa pediatrician and vice president of the Florida chapter of the American Academy of Pediatrics, said the organization opposes both the DeSantis administration proposal to revoke vaccine requirements and the bill that would expand exemptions. Florida’s kindergarten vaccination rate fell from 94% before the pandemic to about 90% in 2024-25, according to the Stateline analysis.

“They’re ignoring the 90% of their constituents who want vaccines and want to stay safe,” said Takagishi. “The legislators are listening to the louder voice of those who want to oppose vaccines instead of the majority. We also know that there are teachers in the school system and school nurses who are fighting this because it puts them at risk.”

All states except Montana report kindergarten vaccine statistics to the federal government. Montana enacted a 2021 law making vaccine status private and unavailable for statistical reports, over the objections of medical experts. The law also made medical exemptions easier for families who think their children have been injured by vaccines.

Dr. Lauren Wilson, a pediatrician and then-vice president of the Montana chapter of the American Association of Pediatrics, said in a hearing that the law would make “vaccination information unavailable for responding to and mitigating public health emergencies.”

“Vaccines have saved millions of lives. I personally have seen cases of tetanus, pertussis, measles and meningitis and the tragedies that these mean for families,” Wilson said in her testimony.

A 2023 court order forced Mississippi to accept religious exemptions. West Virginia allows religious exemptions following the governor’s order last year.

Tibbs, who practices pediatrics in rural Jones County, Mississippi, said she has been seeing more pertussis than usual, and thinks vaccine exemptions could be a factor.

In Mississippi, which reported 394 religious exemptions for the 2024-25 school year, overall rates remained high enough that year, at about 97.8%, to ensure “herd immunity” in most cases.

Mississippi has granted 617 religious vaccination exemptions for kindergartners this school year, about 1.8% of the class, according to Amanda Netadj, immunizations director for the state health department. About 96.3% of kindergartners have all required vaccinations this year.

But the state’s whooping cough cases last year were the highest they’d been in at least decade, and in September health officials announced an infant had died of the disease — the state’s first whooping cough death in 13 years.

“We do have a lot of people getting the religious exemption,” Tibbs said. ”But still, on any given day, the majority of my patients will still get their vaccines. We are keeping our fingers crossed that the numbers stay high enough.”

Stateline reporter Tim Henderson can be reached at thenderson@stateline.org.