2025’s Texas measles outbreak is a lesson in the value of vaccines
Many people have forgotten what the world was like before vaccines hit the scene
A large measles outbreak in Texas demonstrates how quickly the disease can spread when too few people are vaccinated. This warning sign greets patients at an Odessa, Texas, medical clinic.
AP Photo/Julio Cortez
A major outbreak of measles has emerged in Texas. It started in late January and has already left two dead, one of them a child. Few if any of the affected people had been vaccinated. This event — the largest U.S. outbreak in many, many years — highlights what can happen when a large share of kids do not get vaccinated.
Vaccines can limit — or, as with measles, largely prevent — many serious diseases.
The Centers for Disease Control and Prevention, or CDC, recommends that families protect their kids against more than a dozen deadly diseases. These include not just measles but also whooping cough, mumps, rubella (once known as German measles), polio, pertussis, RSV (respiratory syncytial virus) and influenza.
Such vaccines have proven very effective. They also avoid many complications of once-common infections.
For instance, before a measles vaccine became available in 1963, nearly everyone got the highly contagious disease by age 15. And some 400 to 500 people died from it each year, the CDC notes. By 2000, the United States reported it had eradicated measles. Still, periodic outbreaks happen. This is mostly when infected travelers catch the virus and bring it home. Measles can then spread easily among unvaccinated people.
Vaccines have eradicated smallpox. They’ve also eliminated polio and several other diseases from many parts of the world.
But a number of families have interpreted the near absence of some once-common diseases as a sign that vaccines are no longer needed. The new measles outbreak points to why that’s not true.
Science News sat down with two experts to discuss some common concerns and questions about any need for vaccines.
Meet the experts
Aditya Gaur is a doctor who specializes in infectious diseases. He conducts research at St. Jude’s Children’s Research Hospital. It’s in Memphis, Tenn. Before coming to the United States nearly 30 years ago, Gaur worked as a pediatrician in India. This was when few vaccines were available. He and other doctors repeatedly treated cases of measles, he says, along with many other vaccine-preventable ailments.
“I saw tetanus in children … and how uncomfortable it was for children, sometimes leading to death,” he says. In diphtheria patients, he saw “how difficult it can get to breathe. I saw those with pneumonia and air leaks in the lungs — and then the children that died. I’ve seen polio [cause] paralysis.”
Since coming to the United States, Gaur says, he hasn’t seen a single case of any of these diseases. The reason? Vaccines, he says.
Kawsar Talaat is a doctor and vaccine-safety researcher at the Johns Hopkins School of Public Health in Baltimore, Md. Her father had polio as a child. Born before the vaccine was available, “he was paralyzed as a child,” she says. He always had a limp. And when he got older, “he got weaker and weaker and weaker.” Today, she says, “he’s in [a] wheelchair.” So she knows firsthand how polio can be “a lifelong, debilitating illness.”
Talaat has also treated diseases that vaccines can prevent. As a young doctor, she recalls, she would see “waves of children in with dehydration due to rotavirus.” Now those waves are more like ripples. Cases in 2019 were already down 91 percent from pre-vaccine levels.
How vaccines work
At birth, babies get some antibodies from their mothers. For a few months, a mother’s antibodies can give infants some protection against certain illnesses, Gaur says.
That’s why a new vaccine against RSV is now given during pregnancy. It will protect a mom’s newborn. The RSV vaccine only came out in 2023. Before that, this life-threatening illness had been the leading reason for U.S. babies being hospitalized.
As children grow, their immune systems learn to combat illness. One way is by getting and surviving an infection. An easier way: by getting a vaccine.
Vaccines train the body’s immune system to fight off disease. These shots may contain weakened or killed germs. Or they may be just parts of those germs, called antigens. A vaccine doesn’t cause disease. It instead teaches the immune system which invaders to look out for, Gaur explains.
As of March 14, at least 301 people in the United States had come down with measles. Of these, 259 were in Texas (where one child died). This outbreak sent at least 20 people to the hospital. It spilled over the state line to New Mexico, too. There, at least 35 people have caught measles (and one adult died). A few cases of this disease also have turned up in 12 other states this year.
The problem with measles
If a child gets measles, there’s no way to know how serious their case will be, says Gaur. And it can be serious. Measles hospitalized 1,018 people in the United States between 2002 and 2016; 34 went on to die.
Measles also can cause serious complications. These include kidney failure, brain swelling, pneumonia, blood clots and eye problems.
“With vaccines, you are controlling that exposure and teaching the immune system how to fight off an infection,” Gaur points out. Side effects of measles vaccines usually consist of little more than a sore arm and sometimes a fever or mild rash.
Even infections that don’t kill, Talaat notes, may cause serious impacts — ones that vaccines can prevent.
“For most people, chicken pox is mild,” she points out — “but not for everybody. I have seen kids in the hospital with really severe, life-threatening bacterial infections that occurred because their skin was disrupted by chicken pox.” These kids may lose so much skin, it’s as if they were severely burned. “It’s happened in children’s groins. And so their future fertility … [ability to have children may] have been affected.”
And “even if the disease is mild, it still means that that child will miss a week or more of school and that their parent will miss a week or more of work,” she says.
Most cases in the 2025 Texas measles outbreak were children who were unvaccinated or were not known to have gotten a vaccine. That mirrors previous U.S. outbreaks. Of 285 reported cases last year, for instance, nearly nine in every 10 had never gotten a measles vaccine, CDC data show.
U.S. vaccination rates have been falling for measles and other so-called childhood diseases. When more than 95 percent (19 in every 20 people) are vaccinated against measles, there is a community — or “herd” immunity — effect. Keeping most people healthy prevents the disease from spreading to those who can’t be vaccinated (such as people with weak immune systems).
Measles vaccination rates in U.S. kindergartners has fallen from 95.2 percent in the 2019–2020 school year to 92.7 percent in 2023–2024. That left some 280,000 kindergartners at risk of measles during the last school year, according to the CDC.
How protective are vaccines?
Worldwide, since the mid-1970s, vaccines against 14 infectious diseases have saved 154 million lives. That’s the finding of a May 25, 2024, report in The Lancet.
In the United States, routine childhood vaccinations prevented more than 24 million cases of disease in 2019 alone. They included some 1,000 cases of tetanus (also known as lockjaw) and more than 4.2 million cases of chicken pox.
Childhood vaccines protect against a range of viral diseases. They also cover infections caused by bacteria. These include pneumococcal types and Haemophilus influenzae (a bacterium that can cause many types of severe disease in young children). These are all long-lasting vaccines. Some even offer lifetime protection.
And that’s important because some of these diseases can cause lifelong complications — from brain damage and deafness to muscle weakness or partial paralysis.
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Vaccines in older children to prevent HPV (the human papillomavirus) can limit later risk of several cancers. Cervical cancer rates nosedived, for instance, among young women after a childhood HPV vaccine became available.
Some celebrities and political leaders have expressed skepticism about the value of vaccines. And this past January, the Trump administration cancelled meetings of committees that advise the CDC and the U.S. Food and Drug Administration (FDA) about vaccines. Calling off those meetings could threaten the nation’s ability to get updated vaccines for the next flu season.
Tina Tan is a doctor and president of the Infectious Diseases Society of America. Cancelling vaccine advisory meetings and other government efforts aimed at ensuring vaccine safety “puts everyone at risk,” Tan said in a statement. This is especially worrisome, she said, “when we are currently experiencing the worst U.S. flu season in more than a decade.” (At least 41 million people have gotten the flu so far this season. This outbreak has sent an estimated 540,000 people to the hospital and already killed at least 23,000.)
Unlike long-lasting childhood vaccines, doctors recommend yearly shots for flu and COVID-19. Vaccines appear to have stopped 1.2 million U.S. flu cases in 2019. That’s more than one in every eight that likely would have occurred without vaccines. COVID-19 vaccines saved at least 14 million lives globally in the first year they were out.
How the schedule of when to vaccinate developed
Before we ever get shots in our arms, vaccines go through many years of lab and animal tests. Later, there will be several phases of human trials — also called clinical trials.
Medicines and other medical therapies are developed to help sick people. Vaccines aren’t. They’re targeted at still-healthy people. The side effects allowed with many medicines would never be tolerated for vaccines. Says Talaat: “Vaccines pass a higher bar than most treatments.”
Advisers for the U.S. CDC and FDA carefully weigh the benefits and risks of each vaccine against the harms caused by infections. Then they decide whether to recommend kids get a shot — and when. New vaccines have emerged over the past half century, as have data on their impacts. As a result, Talaat says, recommendations for if and when kids need these shots has “happened very gradually.”
“Once we started making vaccines, children were a natural target [for them],” she adds. Why? Kids are most at risk for a lot of these infections. For instance, rotavirus causes diarrhea that can easily dehydrate young children and land them in the hospital. So babies typically get this vaccine when they are 2 months old.
Pertussis vaccines are also among the earliest given because “the younger the baby, the more susceptible they are to [whooping cough],” Talaat says. “Their airways are so small that they’re more likely to die from it.”
For measles, Talaat says, “there’s a sweet spot when you want to get the vaccine into kids to protect them. But,” she adds, “you don’t want to give it too early.” The reason? Antibodies passed from the mother to the baby can interfere with this vaccine. So the first combo shot for measles, mumps and rubella tends to be given when babies are 12 to 15 months old.
When there are big outbreaks, however — like the one this year in Texas — babies as young as 6 months might get the shot. That’s important if their mothers haven’t been vaccinated and didn’t have protective antibodies to pass on.
Vaccines that protect against HPV and meningococcal disease aren’t given until kids are preteens or teenagers. That’s because adolescence is when they are at higher risk of infection.
Can kids safely get many vaccines at once?
Many childhood vaccines protect against multiple diseases in a single shot. These include one that combines polio, diphtheria, tetanus and pertussis, hepatitis B and Haemophilus influenzae type b. Another guards against up to 20 strains of pneumococcal bacteria. A 2-month-old might get a couple of shots that together protect them from more than two dozen types of infections. (The rotavirus vaccine is given as a drink.)
“We have done studies that show that giving these vaccines together is safe,” Talaat says. And, she adds, this doesn’t affect the immunity these shots offer.
“We are exposed to lots of things every day in our environment. Our bodies and our immune systems are built to handle that,” she points out. “And when we get multiple vaccines and multiple antigens at the same time, our bodies can handle that, too.”
The most common complaint from getting a vaccine is a sore arm (as most vaccines are given as shots). “Anything which is injectable may cause an immediate owie,” Gaur says — and then some swelling and tenderness. Depending on the vaccine, other mild side effects might also show up. Among them: fever, fatigue, muscle or joint pain and maybe a rash.
In rare cases, severe side effects may occur. An allergic reaction is one example. Certain people face a higher risk of problems. For instance, adolescent and young adult males are more likely than other people to develop an inflammation of the heart or the sac around the heart after a COVID-19 vaccine. But getting a COVID-19 infection is more likely to cause those heart problems than the vaccine is. And the vaccine can prevent severe disease. So government officials have calculated that the benefits of COVID-19 vaccinations outweigh the low risks.
