Last week, the U.S. Centers for Disease Control and Prevention changed the language on a vaccine safety webpage, appearing to legitimize the long-disproven link between childhood vaccines and autism. The switch has sparked confusion among parents, as experts say it contradicts decades of scientific research and consensus.

“It goes against everything we’ve learned from countless peer-reviewed studies and the health data of millions of children,” Dr. Paul Offit, a pediatrician and director of the Vaccine Education Center at the Children’s Hospital of Philadelphia, tells TODAY.com.

The new language and its widespread media coverage have left many parents wondering: What changed? Has new research come out? Should I be worried?

Doctors tell TODAY.com the answer is clear: The science hasn’t changed at all.

What has changed, they say, is that since Health and Human Services Secretary Robert F. Kennedy Jr. — a longtime anti-vaccine activist — has taken office, they’ve seen an increase in confusion among parents, especially due to social media.

Also contributing, experts say, are new scrutiny of the childhood vaccine schedule under Kennedy and President Donald Trump, the dismissal of a prominent, independent vaccine advisory committee and the cherry-picking of vaccine data displayed on the CDC site.

HHS spokesman Andrew Nixon told NBC News that the website had been updated “to reflect gold standard, evidence-based science,” but did not immediately answer a follow-up question about how the agency defines such science.

According to the newly updated webpage, the assertion that “vaccines do not cause autism” is not “evidence-based,” and “studies supporting a link have been ignored by health authorities.” But other pages on the CDC site still reflect the fact that hundreds of scientific studies have found no relationship between autism and vaccines.

In an interview with The New York Times, Kennedy said he requested the change because “the whole thing about ‘vaccines have been tested and there’s been this determination made,’ is just a lie.” However, pediatric and vaccine experts say that autism is one of the most studied childhood conditions, and no high quality research has ever found a link to vaccines.

“We all used to look to the CDC for medical guidance and direction,” Offit says. “Most people in the scientific and medical communities are now ignoring it completely.”

Adds Dr. Scott Hadland, chief of adolescent medicine at Mass General Brigham for Children: “I’ve absolutely seen an uptick in (vaccine) questions in recent weeks. Families come in feeling torn between what they’re reading online and what their doctors are telling them, and that erosion of trust can be hard to repair.”

Dr. Edith Bracho-Sanchez, primary care pediatrician at Columbia University Irving Medical Center, agrees that “vaccine hesitancy has, without a doubt, increased in my practice since RFK became the Secretary of Health and Human Services.”

“He has repeated debunked links between vaccines and autism to a broader audience, which, from his position of power, has served to legitimize them,” she tells TODAY.com.

Offit points to what he says are some major consequences of anti-vaccine rhetoric: The U.S. is on the verge of losing its measles-elimination status; the 2024-2025 flu season saw 280 pediatric deaths mostly in unvaccinated children, the highest since the influenza pandemic of 2009; and measles vaccination rates have dipped below the 95% threshold needed for herd immunity.

So what does all this mean for doctors on the ground? What conversations are they having with concerned parents? Here’s what they’re hearing and how they’re responding.

Parents’ Top Questions About Vaccines and Autism

“Is there any chance vaccines trigger autism?”

“If the science is clear, why do some people keep saying there is a link?”

“What should I look for if I think my child is showing early signs?”

These are all questions Dr. Ilan Shapiro, a pediatrician at AltaMed Health Services in Los Angeles, has been hearing lately.

“I have seen a rise in questions as parents tell me they are hearing mixed information from public conversations, social media and national news,” he tells TODAY.com. “That creates confusion and worry, and families come in stressed and looking for clarity.”

His response to such questions is to focus on reassurance and evidence. “I bring the discussion back to what we know from science and from caring for millions of vaccinated children,” he explains. “That evidence shows that vaccines protect, they save lives, and they do not create autism.”

Timing of Vaccines and Autism Symptoms

Dr. Alison Mitzner, a pediatrician and chair of a New York American Academy of Pediatrics chapter, says a question she’s hearing more is: Why do signs of autism seem to occur soon after a child receives an MMR (measles, mumps and rubella) vaccine?

“I respond by validating that the apparent timing can be confusing,” she tells TODAY.com. “But then I explain that when this occurs, it’s correlational, not causal.” The correlation happens simply because signs of autism typically emerge around 1-2 years of age, the same age most kids receive the shot.

She adds that we now have over two decades of data tracking autism rates in kids who have received the MMR vaccine, “and the science is absolutely clear: MMR does not cause autism.”

Giving Multiple Vaccines at Once

Bracho-Sanchez says the question of whether it’s safe to give multiple vaccines at once has also been popping up. In response, she explains that vaccines have been extensively studied both individually and together and that it is safe to get multiple vaccines at once.

“Many (parents) don’t realize that children are exposed to a significantly higher amount of antigens, the foreign substances that trigger the immune system, in their daily lives than they ever will be through vaccines,” she adds.

Safety of Vaccine Ingredients

Dr. Heather Viola, a primary care physician at Mount Sinai Doctors-Ansonia in New York, tells TODAY.com that she, too, is getting a surge of questions about the safety of vaccines, particularly about vaccine ingredients aluminum and thimerosal.

Aluminum is a naturally occurring metal used in tiny amounts to help vaccines create a stronger and longer-lasting immune response. It isn’t worrisome, Viola tells parents, because it is processed quickly by the body, has never been known to cause autism, and the amount used is so small that it’s even “less than babies ingest through formula or breast milk.”

Thimerosal is a mercury-based preservative that is used in some vaccines, though it has not been used in childhood vaccines since 2001, according to the CDC.

Viola notes that many parents are understandably concerned about the possibility of mercury poisoning, but they don’t know there are two types of mercury, methylmercury and ethylmercury, and the latter, used in thimerosal, is much less likely to build up in the body and has been proven to be safe.

“Extensive testing shows these ingredients are safe and not linked to autism,” she stresses.

“Did Vaccines Cause My Child’s Autism?”

Hadland tells TODAY.com that one of the most heartbreaking questions he now receives from parents of a child diagnosed with autism is: “Did I cause my child’s autism by giving them vaccines?” After he helps them understand that no, they did not, the next question is often, “Then what does cause autism?”

Scientists don’t have one single answer, he says, but the evidence overwhelmingly supports a mix of genetic factors, prenatal and early-development influences, and complex brain-development pathways. But one thing researchers know for certain is that vaccines are not the culprit.

“We are as certain of this fact as we are of the fact that smoking causes lung cancer,” says Hadland. “Decades of rigorous studies, including research following millions of children, show that vaccines do not cause autism.”

Misinformation Leads to Fewer Questions, More Refusals

In some areas, doctors say they are actually receiving fewer questions about vaccines, which they attribute to the onslaught of misinformation online and elsewhere.

“Unfortunately, I don’t get a lot of questions about vaccines and autism,” Dr. Michael Fullmer, a pediatrician at Utah Valley Pediatrics in Saratoga Springs, Utah, tells TODAY.com. Instead, parents simply tell him they don’t want to vaccinate because they fear autism.

“They have already done their ‘research,’ and they have already made up their mind,” he says. “And these are parents that I have a good relationship with. They have brought all of their children to me for their health care, and they seem to trust me with everything except vaccines.”

Dr. Khadijia Tribié Reid, pediatric medical director at MedNorth Health Center in Wilmington, North Carolina, tells TODAY.com she has “absolutely seen increased vaccine hesitancy” in recent months.

“I hear statements like, ‘I don’t want to inject something into my baby’s little body,’ ‘I don’t know what’s in the vaccine,’ ‘When is the last time anyone has gotten polio?’ and ‘I didn’t have anything like (hepatitis B), so we don’t need that vaccine right now.’”

She says she believes families no longer fear the diseases that vaccines prevent because they’ve been so effective that people don’t know what those illnesses were like. “Vaccines are a victim of their own success,” she adds.

As Offit puts it, “we didn’t just eliminate measles from this country. We eliminated the memory of measles. … People forgot how sick or dead that virus could make you.”

For parents unaware of the dangers of vaccine-preventable illnesses, “I explain the risks of the illnesses themselves,” Bracho-Sanchez says. “I tell them that vaccines are, without a doubt, necessary if our goal is to protect children from these and other dangerous illnesses.”

It’s a point echoed by Hadland, who reminds families that they’re not alone in wanting what’s best for their kids.

“Ultimately, all parents are just looking to do what’s right for their children,” he says, adding that this is exactly why more parents should want to vaccinate their children, not less.

“The science hasn’t changed. Vaccines are safe, effective and critical for keeping kids healthy.”