A page of the Centers for Disease Control and Prevention's website was changed to include a false claim about autism and vaccines. Multiple CDC officials familiar with the situation said the change was made by political appointees inside the Department of Health and Human Services without input from relevant agency staffers.

The page about vaccines and autism formerly said that "no links have been found between any vaccine ingredients and Autism spectrum disorder." The website has now been changed to say, "'Vaccines do not cause autism' is not an evidence-based claim" — a statement the Autism Science Foundation calls "misinformation" that "actually contradicts the best available science." The CDC page also falsely claims that studies supporting a link between vaccines and autism have "been ignored by health authorities."

Previously, changes have only occurred in consultation with subject matter experts at the agency's National Center on Birth Defects and Developmental Disabilities and its National Center for Immunization and Respiratory Diseases. The CDC sources told CBS News political appointees at HHS devised the change and instructed an employee inside the office of acting CDC Director Jim O'Neil to make it.

Autism is a developmental disability caused by differences in the brain. It presents with a wide range of symptoms that can include delays in language, learning, and social or emotional skills. The National Institutes of Health has committed hundreds of millions of dollars a year to studying the condition and trying to understand how and why it develops.

The debunked theory that the measles, mumps and rubella vaccine causes autism has its roots in a 1998 study that was found to be fraudulent and has been retracted. Since then, "independent researchers across seven countries have conducted more than 40 high-quality studies involving over 5.6 million people," said American Academy of Pediatrics president Susan Kressly in a statement decrying the website change.

"We are at a very dangerous moment for the health of America's children," said Dr. Sean O'Leary, chair of the AAP's Committee on Infectious Diseases, in a news briefing on Thursday.

Research has found no evidence of increased rates of autism among those who are vaccinated compared to those who are not. Vaccines also undergo intensive safety testing. Research shows that genetics play a role in autism diagnoses. The NIH says some possible risk factors for autism include prenatal exposure to pesticides or air pollution, extreme prematurity or low birth weight, certain maternal health conditions, or parents conceiving at an older age.

"There is overwhelming evidence that vaccines do not cause autism," said Dr. Mandy Cohen, a former CDC director. "This change to CDC language undermines the agency's scientific integrity, damaging its credibility on vaccines and other health recommendations. Most concerning, it risks endangering children by driving down vaccination rates and leaving kids vulnerable to preventable diseases like measles and whooping cough."

In a statement, HHS communications director Andrew Nixon said, "This is a common-sense update that brings CDC's website in line with our commitment to transparency and gold standard science.

"As the updated page explains, the claim that 'vaccines do not cause autism' is not supported by comprehensive evidence, as studies to date have not definitively ruled out potential associations. Some research suggesting possible biologic mechanisms has been ignored or dismissed by public health agencies, and HHS is committed to finding a definitive answer," Nixon said.

Leading autism advocacy groups dispute that. The Autism Science Foundation said in a statement it was "appalled" by the change to the CDC's website, and highlighted the decades of research into the topic. Alison Singer, the co-founder and president of the ASF, said that while researchers "can't do a scientific study to show that something does not cause something else," there are a "mountain of studies that we have exonerating vaccines as a cause of autism."

"I think the question of whether vaccines causes autism is one that science can answer, and science has answered it," Singer said in Thursday's news briefing.

A subhead saying that "Vaccines do not cause autism" remains on the CDC website with an asterisk next to it. The bottom of the page explains that the header remains in place because of an agreement with Louisiana Republican Sen. Bill Cassidy, a physician who is the chair of the Senate Health, Education, Labor, and Pensions Committee and backed HHS Robert F. Kennedy Jr. during his confirmation hearings. Cassidy said Sunday on "Face the Nation with Margaret Brennan" that he supported Kennedy in part because of "serious commitments" from the Trump administration, but did not specify what those were.

"I'm a doctor who has seen people die from vaccine-preventable diseases," Cassidy wrote on social media on Thursday afternoon. "What parents need to hear right now is vaccines for measles, polio, hepatitis B and other childhood diseases are safe and effective and will not cause autism. Any statement to the contrary is wrong, irresponsible, and actively makes Americans sicker."

Cassidy highlighted recent outbreaks of whooping cough and measles. He also called for more research into "the real causes of autism," and criticized HHS funding cuts.

"Redirecting attention to factors we definitely know DO NOT cause autism denies families the answers they deserve," Cassidy wrote.

Other health agency pages with information about autism and vaccines had not been changed as of early Thursday afternoon.

Kennedy has previously pushed the discredited claim that routine childhood shots cause autism. President Trump has also falsely suggested vaccines could be to blame for autism rates. Both expressed concern about rising rates of autism diagnoses, which appear to be driven by a variety of factors including increased awareness and changes in how the condition is diagnosed.

O'Leary said he feared the website changes would "scare parents and further stigmatize" people with autism.

"We have been dealing with these falsehoods for many years. They are not new. We have been promoting the science, and we're going to continue to do that, as are the other professional societies," he said. "The problem is now it's coming from, these falsehoods are coming for our federal government."

Experts have previously raised concerns about Kennedy reviving debunked theories about the cause of autism. In April, Kennedy announced the CDC would conduct a "massive testing and research effort" to find out what causes the disorder, and hired David Geier, a man who repeatedly claimed a link between vaccines and autism, to lead the effort. Kennedy said the work would be completed by September, though other health officials later pushed the timeline.

Dr. Fiona Havers, an infectious disease physician and former CDC official, said that the website change showed scientists "who in the past carefully vetted scientific information have been pushed aside."

The "CDC should be a data-driven agency based on science and not ideology, but when you take the scientists out of the process you get rhetoric that can harm families," said former CDC chief science and medical officer Dr. Debra Houry, who lresigned from the agency earlier this year.

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