Scientists at the Centers for Disease Control and Prevention were stunned this week after the agency quietly rewrote long-standing language on vaccines and autism, adding false information that has been extensively debunked.

The CDC’s website, once unequivocal that studies show “no link” between childhood vaccines and autism, now carries a very different message.

The updated page says the statement “vaccines do not cause autism” is “not an evidence-based claim,” falsely arguing that research has “not ruled out the possibility that infant vaccines contribute to the development of autism.”

It also incorrectly states that public health authorities have “ignored” studies pointing to a supposed connection. That framing mirrors arguments long pushed by one of the country’s most prominent anti-vaccine advocates: Health and Human Services Secretary Robert F. Kennedy Jr., who oversees the CDC.

Inside the agency, the fallout was immediate. Five CDC officials told The Washington Post they had no warning about the changes and played no role in drafting them. They requested anonymity out of fear of retaliation—a sign of how fraught the science-policy boundary has become inside an agency now run by a committed vaccine antagonist.

To some former officials, the rewrite confirmed their worst suspicions. Dr. Demetre Daskalakis, who led the CDC unit overseeing respiratory viruses and immunizations before resigning in August, told the Post the new language shows the agency “cannot currently be trusted as a scientific voice.”

“The weaponization of the CDC voice by validating false claims on official websites confirms what we have been saying,” he added.

The shift is all the more jarring given the mountain of research behind the original guidance. Dozens of peer-reviewed studies have found no association between autism and the mumps, measles, and rubella vaccine. A Danish study of more than 1.2 million children published this year similarly found no link between aluminum in vaccines and any neurodevelopmental harm.

The false link between vaccines and autism stems from a now-retracted 1998 article in The Lancet, an esteemed medical journal. Despite that retraction and decades of studies debunking it, the anti-vaccine conspiracy theory endures—thanks in large part to Kennedy and, at moments, President Donald Trump, who has floated baseless speculation about autism and Tylenol use during pregnancy.

Even the CDC page’s header, which says “Vaccines do not cause autism,” now carries an asterisk noting it remains only because of an agreement with Louisiana Sen. Bill Cassidy, a medical doctor and the Republican chair of the Senate Health, Education, Labor, and Pensions Committee. Cassidy secured the commitment during Kennedy’s confirmation process, pressing the nominee to preserve federal vaccine guidance.

On Thursday, Cassidy issued a statement condemning the new CDC guidance.

”I’m a doctor who has seen people die from vaccine-preventable diseases. 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,” he said.

Publicly, HHS insists the overhaul is rooted in “gold standard, evidence-based science,” as spokesperson Andrew Nixon told Axios.

Former officials aren’t buying it. Dr. Debra Houry, the CDC’s former chief medical officer—who also resigned in August—questions how the new language that “misrepresents decades of research ended up on a CDC website.”

Public health communication, she added to the Post, must be “accurate, evidence-based, and free from political distortion. Anything else erodes trust and puts lives at risk.”

Outside the agency, anti-vaccine activists celebrated the shift. Children’s Health Defense, the group formerly led by Kennedy, declared that the CDC is finally “beginning to acknowledge the truth” and “disavowing the bold, long-running lie that ‘vaccines do not cause autism.’”

That embrace underscores what’s at stake. A federal health agency once known for its methodical caution is now echoing rhetoric that science overwhelmingly rejects. With Kennedy shaping the message, the country’s most important public health voice is inching toward fringe territory—and millions of Americans may pay the price.

Reprinted with permission from Daily Kos