In Texas, dozens of children have contracted measles in the state’s largest outbreak in 33 years. Online, some are blaming vaccines for the disease’s spread.

“Measles cases surge 2,042% in Texas County following free vaccine campaign— coincidence or connection?” read what looked like a headline screenshot featured in a Feb. 19 Facebook post. “Gaines County, Texas, is experiencing a staggering 2,042% spike in measles cases — right after a public health initiative distributed free measles vaccines.”

Gaines County is experiencing an alarming measles outbreak. And its health officials did launch a vaccine drive. But the post gets its numbers wrong and misleads about the nature of the measles vaccine: It is highly effective, and vaccinated people are far less likely to contract or spread the disease.

(Screenshot/Facebook)

The Facebook post was flagged as part of Meta’s efforts to combat false news and misinformation on its News Feed. (Read more about our partnership with Meta, which owns Facebook and Instagram.)

The post’s claim originated in a Feb. 17 article from The People’s Voice, a website known for spreading misinformation.

“There is no evidence that the measles vaccine can spread to other people. It is not contagious,” Raul Andino-Pavlovsky, professor of microbiology and immunology at University of California, San Francisco, told PolitiFact.

What is measles and why is it on the rise?

Measles is a highly contagious viral infection that can cause fever, rash, coughing, ear infections, pneumonia and death. It spreads through the air when an infected person coughs or sneezes and is especially transmissible among children, according to the U.S. Centers for Disease Control and Prevention. In 2000, measles was declared eliminated in the U.S. after more than a year without continuous spread, a development that health officials attributed to a highly successful vaccine campaign.

But large measles outbreaks can occur when the virus crosses borders and reaches unvaccinated or undervaccinated communities, the CDC said. Increasing vaccine hesitancy rates contribute to outbreaks.

In late January, Texas reported two measles cases in Houston’s Harris County. The cases involved two people in the same household who had traveled internationally and were not vaccinated.

As of Feb. 28, the number of reported infections had increased to 155 across nine Texas counties and eastern New Mexico, including an unvaccinated school-aged child who died after being treated at a Lubbock, Texas, children’s hospital. Of the 146 Texas-only cases, five people were vaccinated. The rest were either classified as unvaccinated or their vaccination status was unknown, the Texas Department of State Health Services said.

Measles and vaccines in Gaines County

Gaines County’s case numbers led all the other counties with 98 — not “200 or 300” as the Facebook post said — a 1,533% rise from the six cases it reported Feb. 5. On Feb. 14, NBC News said health officials’ estimated that another 200 to 300 people were infected across West Texas — not Gaines County alone — but haven’t been tested.

“There are people who are in the process of being tested and evaluated for measles in West Texas but there are not 200-300 people waiting on testing at this time,” Lara Anton, Texas Department of State Health Services spokesperson, told PolitiFact in a Feb. 27 email. “We expect that the number of cases will continue to increase because the virus is highly contagious and 90% of unvaccinated people will get it.”

Anton said the department does not provide counts of suspected cases.

Gaines County’s public schools last year had one of the state’s highest vaccine exemption rates, with more than 17% of its students citing reasons of conscience for not receiving one or more required vaccinations.

The People’s Voice cited South Plains Public Health District vaccination clinics held Feb. 6 and 7 in Gaines County.  On Feb. 5, the Texas state health department confirmed Gaines had six cases of measles, “all among unvaccinated school-aged children.”

But there is no information that suggests such vaccines would accelerate infection spread — it curbs it. Claims otherwise stem from a misunderstanding of “vaccine shedding.” The Measles, Mumps and Rubella (MMR) vaccine is a two-dose attenuated (weakened) live virus vaccine. According to the CDC, the virus causes a harmless infection in the vaccinated person’s body that causes very few, if any, symptoms. The immune system responds to the infection and the body develops immunity.

Although it is possible for vaccinated individuals to “shed” the virus in their urine and stool, experts told PolitiFact the measles vaccine would not transmit the disease to other people. Anton told NBC News that all samples tested in the outbreak were identified as a known wild measles strain, not a vaccine strain.

Paul Offit, Children’s Hospital of Philadelphia Vaccine Education Center director, said the measles vaccine virus is “too attenuated to be passed from one person to the next.”

Matthew Washam, assistant professor at Ohio State University College of Medicine’s Department of Pediatrics and co-writer of a 2024 article about measles vaccine shedding in children, said vaccines don’t cause outbreaks as the post said.

“This shedding is not contagious to others, and does not lead to measles outbreaks,” he said.

Live virus vaccines are not recommended for all people. Cancer patients, for example, and others who are immunocompromised may not have the ability to fight the virus, even in the vaccine’s weakened form.

Andino-Pavolvsky said a small number of people who receive the vaccine may develop mild rashes, but they would not be contagious and would pose no risk to others. Philip Keiser, a University of Texas Medical Branch global health professor, told PolitiFact there’s no scientific literature supporting the notion that a vaccine virus shed from someone who is vaccinated would be transmissible.

“The MMR vaccine (measles, mumps, and rubella) is the best and most reliable way to protect against these serious diseases,” Andino-Pavolsky said. “It has been widely studied and is considered one of the safest and most effective vaccines ever developed.”

We rate the claim that the Texas’ Gaines County’ measles outbreak was caused by “a public health initiative” to “distribute free measles vaccines” False.

This fact check was originally published by PolitiFact, which is part of the Poynter Institute. See the sources for this fact check here.