The Centers for Disease Control and Prevention was ordered to shelve promotions it developed for a variety of vaccines, including a "Wild to Mild" advertising campaign urging people to get vaccinated against flu, two sources familiar with the decision told STAT.

The Department of Health and Human Services' assistant secretary for public affairs informed the CDC that HHS Secretary Robert F. Kennedy Jr. wanted advertisements that promote the idea of "informed consent" in vaccine decision-making instead.

Informed consent is the principle that people should be notified of all the risks, as well as benefits, of any medical intervention they receive or any drug they are prescribed. It is a cornerstone of health care delivery.

Shifting the framing of advertising for vaccines that the CDC has long recommended -- like flu shots -- to more heavily focus on the risks of vaccines could undermine people's willingness to get vaccinated, or to have their children immunized.

"Informed consent is always a must," said Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy. But he suggested generating materials that focus heavily on possible risks without putting them in the context of proven benefits could badly hurt vaccination rates in the country.

The decision to pull flu shot advertising is an early sign of how RFK Jr. may shift the U.S. approach to vaccinations as the nation's top health official. Others came Thursday as well: The CDC's influential vaccine advisory committee postponed a meeting scheduled for next week, and Politico reported that RFK Jr. may remove some members of that committee and other influential public health bodies, claiming they have conflicts of interest.

STAT asked HHS whether the CDC had been instructed to cease promotional campaigns for several vaccines, including the Wild to Mild flu vaccine campaign, and whether the HHS secretary wanted replacements that focus on informed consent.

In an emailed response, an official did not answer the second question, and denied that the CDC had been told to take down its flu vaccination campaign website -- which was not the question asked.

"No, the CDC was not told to take down the flu vaccination campaign webpage," said an HHS spokesperson. "Unfortunately, officials inside the CDC who are averse to Secretary Kennedy and President Trump's agenda seem to be intentionally falsifying and misrepresenting guidance they receive."

The CDC's own informational pages on the benefits of flu shots still remain. The materials that sources told STAT they were instructed to take down were for paid promotions on other websites. Versions of those promotions were previously visible on some CDC webpages but are no longer up.

"Flu vaccination can keep you from getting sick with flu," one of the remaining pages states. "Flu vaccine prevents millions of illnesses and flu-related doctor's visits each year."

In the wake of the Covid-19 pandemic, uptake rates for a number of vaccines have declined. About 23% of adults have received an updated Covid-19 shot. And though this flu season has been protracted, about 45% of people have received a flu vaccine this season -- down about five percentage points from flu shot uptake in the pre-Covid era.

Kennedy, who has generated substantial income from challenging the safety of vaccines -- through paid speeches, books, his former position as founder and chair of Children's Health Defence, and as a lawyer suing vaccine manufacturers -- refused repeatedly during his Senate confirmation hearings to distance himself from disproven claims about the safety of vaccines, such as the claim that vaccines are behind rising autism rates. At the same time, he said during the hearing that he is not opposed to vaccines.

Though several senators expressed concern about Kennedy's positions on vaccines, only former Senate leader Mitch McConnell (R-K.y.), a survivor of polio, voted against Kennedy's confirmation on the Republican side of the chamber.

Sen. Bill Cassidy (R-La.) expressed serious concerns about Kennedy during the hearings on his nomination. Cassidy is a physician who strongly supports vaccination. But in the end he voted for Kennedy after receiving assurances that Kennedy would work within the current system and not undermine vaccination efforts in the country.

The promotional campaigns the CDC was ordered to stop involved modest outlays of money, one source told STAT. They included paid ads in digital publications or promoted posts on social media platforms, the individual said. NPR reported earlier that the "Wild to Mild" campaign was halted.

The ads featured images of fierce and less threatening animals -- one juxtaposed a teddy bear against a grizzly -- to convey the message that even if flu vaccines do not always prevent infection, people who receive them are less likely to become seriously ill and to need hospital care.

"Flu can be wild. But a flu vaccine can shield both you and your cub from flu's more serious symptoms," said one of the ads, aimed at pregnant people. "Ask your health care provider about a flu shot during your pregnancy to protect your baby after birth -- when they're too young to be vaccinated."

Other iterations of the campaign were aimed at parents, adults with chronic conditions, people over the age of 65, and health care professionals.

In the materials viewable on a now scrubbed webpage there was no discussion about risks from flu shots.

There are few side effects from flu vaccination, and those that are reported -- things like injection site reactions, headaches and fatigue -- are short lived. In some, though not all, years, flu vaccination appears to be linked to a slightly higher risk of developing Guillain-Barré syndrome, a form of progressive and generally temporary paralysis. In the seasons when an increase of GBS has been seen it is at a rate of about one or two additional cases per one million doses of flu vaccine administered.

Being infected with the flu is known to increase the risk of developing GBS as well.Ensuring that people are aware of the risks of vaccines before receiving them is one of the six parts of a vaccine safety plan that RFK Jr. published in 2023. Already, people receive printed information with the risks of vaccines before they or their children are immunized, and advertising for specific vaccines is required to disclose side effects.