As the largest measles outbreak in the U.S. in 25 years spreads, health experts warn that more people choosing to be unvaccinated for infectious diseases will make it harder to replicate past successful responses to outbreaks.
Measles, a respiratory virus, was effectively eliminated in 2000, when the U.S. only saw 86 cases. According to the Centers for Disease Control and Prevention, an estimated three to four million people in the U.S. were infected with measles and an estimated 400 to 500 people died from the disease each year before the vaccine became available in 1963.
But an outbreak in Texas that has spurred 309 cases as of March 21 and one death of a school-aged, unvaccinated child so far has spread throughout the country. New Mexico, too, has seen a spike in cases, with 42 people identified as having measles and one unvaccinated adult dying as of March 21, according to the New Mexico Department of Health.
In West Texas, where the outbreak began, officials are urging community members to get vaccinated.
“There’s a reason why measles was declared eliminated in 2000 in the United States,” said Phil Huang, the director of Dallas County Health and Human Services, at a March 18 media briefing. “It is because we have a really effective and safe vaccine that works.”
U.S. health officials have had success in dealing with past measles outbreaks. But as the share of unvaccinated individuals increases, it will be harder to replicate those successful responses to outbreaks.
In March 2024, Chicago saw a measles outbreak that led to 57 cases. According to Simbo Ige, commissioner of the Chicago Department of Public Health, it took 30,000 vaccinations to control the spread of the disease.
“Measles thrives when we have people who are unvaccinated. Measles is not able to spread if everyone is protected. If you have a fence in your house, it is harder for there to be a break in,” Ige said at the March 18 briefing. “So we are worried about the resurgence of measles, because over time, more and more people have chosen not to be vaccinated, and so we now have a pool of people who are vulnerable to measles.”
Congressional worries
While state and local health officials are focused on vaccination, members of Congress are urging Health and Human Services Secretary Robert F. Kennedy Jr. to launch a nationwide vaccination campaign and to push back against misinformation about the measles, mumps and rubella (MMR) vaccine.
“We are troubled that anti-vaccine misinformation, cuts to the Centers for Disease Control and Prevention (CDC) workforce, and reductions of public health funding will threaten the country’s ability to respond to the current measles outbreak, and future public health threats,” said a group of Texas Democrats in a March 19 letter to acting CDC director Susan Monarez, who President Donald Trump announce he would nominate to head the agency on Monday.
Kennedy, who has previously embraced widely debunked theories that vaccines cause autism, wrote an op-ed published March 2 on Fox News that acknowledged vaccines prevent infection and recommended unvaccinated individuals get the shot, but nonetheless called the decision to vaccinate “a personal one.”
William Moss, a professor at Johns Hopkins University’s Bloomberg School of Public Health and the executive director at the International Vaccine Access Center, said Kennedy’s comments undermined the messaging on vaccines that the federal government should be giving.
The messaging from the federal government, state and local health officials, he said, “should be really simple about getting measles vaccination.”
Members of Congress are also concerned about an effective measles response amid the terminations of career employees at the CDC.
In a March 14 letter to Kennedy, a group of seven Democratic senators asked him for answers about how those firings are affecting public health preparedness activities including for measles and bird flu outbreaks.
“These actions have not only led to unnecessary turmoil, fear, and chaos for public health officials, experts, and employees at the CDC, they also threaten our national security and disrupt our economy,” the senators wrote. “The mass firings and instability at the CDC could directly impact public health initiatives in our states, particularly in responding to disease outbreaks and funding local health programs.”
Trust in public health
As the share of unvaccinated individuals has gone up, an increase in vaccine skepticism and declining trust in public health institutions will pose serious difficulty in addressing further outbreaks of measles and other infectious diseases.
Moss said that the U.S. withdrawal from the World Health Organization and undermining of confidence in measles vaccines in the U.S. remain among his biggest concerns not just for stopping this outbreak, but preventing future ones.
“In the end, what we’re going to see are larger and more frequent measles outbreaks here in the United States,” Moss said.
Liz Hamel, the vice president and director of public opinion and survey research at health care think tank KFF, said that current trends of vaccine skepticism are a continuation from the COVID-19 pandemic, but it’s too soon to be able to look at trends in public opinion of vaccines and trust in public health institutions from the current measles outbreak.
“We can’t really draw direct causality to the current outbreak and some of the trends we’re seeing, but I do think the trends do suggest some challenges for addressing any infectious disease outbreak in the U.S.,” Hamel said.
According to a Jan. 28 tracking poll from KFF, the share of people who say they trust the CDC “a great deal” or “a fair amount” to make the right recommendations on health dropped slightly from 66 percent in June 2023 to 61 percent in Jan. 2025. When it comes to state and local public health agencies, trust fell from 64 percent to 54 percent.
“Most of the public and most parents still believe that the benefits of the MMR vaccines outweigh the risks,” Hamel said. “They still support vaccine mandates in school, and most parents say that they keep their children up to date on vaccines, but what we saw in the most recent poll is that, for the first time, we found an increase in the share of parents saying that they think the risks of these vaccines outweigh the benefits.”
When the U.S. saw an increase in measles in 2019 from an outbreak of more than 900 cases from an Orthodox Jewish community in New York, an aggressive vaccination campaign prevented a death from the disease. The city of New York spent more than $6 million and dedicated more than 500 staff to the response.
But in West Texas where the outbreak has grown, increasing vaccination rates has been a struggle, according to Katherine Wells, the director of public health in Lubbock, Texas. Wells said at the March 18 briefing that although there has been success in getting more people vaccinated, it has been slow. The county has been working with schools to set up pop-up vaccine clinics to encourage vaccinations.
The outbreak in Texas originated in a Mennonite community after an unvaccinated individual brought measles in from outside of the country. According to Moss, while there are many small outbreaks across the U.S., tight-knit religious communities are ripe for the spread of infectious diseases like measles.
“Think about a forest fire with sparks shooting out, and if those sparks land in a conducive environment for measles virus that’s a susceptible population or a low vaccine courage population, you’re going to get another outbreak,” Moss said.
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