President-elect Donald Trump said he will nominate Robert F. Kennedy Jr., the nephew of former President John F. Kennedy, to be the next health and human services secretary, a move with major implications for the federal public health infrastructure.

The nomination is likely to spur a major confirmation battle in the Senate.

Trump said in a tweet that Kennedy will restore federal health agencies to “the traditions of Gold Standard Scientific Research, and beacons of Transparency, to end the Chronic Disease epidemic, and to Make America Great and Healthy Again!”

Kennedy ran for president as an independent candidate largely on a public health platform, including remodeling the National Institutes of Health and the Centers for Disease Control and Prevention, before dropping out and endorsing Trump.

Trump said in October that he would let Kennedy “go wild on medicines” and food policy in his administration.

“He wants to do some things, and we’re going to let him get to it,” Trump said of Kennedy in his election victory speech. “Go have a good time, Bobby.”

But even before suspending his campaign, Kennedy had a phone conversation with Trump this summer, during which they talked about changing the vaccine schedule for children. Kennedy said he wanted to lower the doses of each vaccine to prevent babies from changing “radically.”

Kennedy eventually dropped out of the race to join Trump as an adviser under the banner of “Make America Healthy Again,” specifically targeted at the obesity epidemic, the high chronic disease burden in the United States, and vaccines that Kennedy says are unsafe and untested.

At a recent event in Scottsdale, Arizona, Kennedy said that, on Day One of the new Trump administration, 600 NIH employees would be fired and immediately replaced.

As the director of the vaccine-skeptical group Children’s Health Defense, Kennedy has long been an advocate of claims that vaccines are a leading cause of autism spectrum disorder and other chronic neurological and autoimmune conditions.

One of his most recent lines of attack against vaccines, and one that has gained the most traction among his populist supporters, is that they have not been “tested in pre-licensing, placebo-controlled trials.” The federal public health establishment, including the former director of the National Institute for Allergy and Infectious Diseases, Dr. Anthony Fauci, have rejected that claim.

Kennedy has also said he is concerned about the financial incentives for large pharmaceutical companies to push unnecessary vaccines on children.

“There’s no downstream liability, there’s no front end safety testing, that saves them a quarter-billion dollars,” Kennedy said at a campaign speech at Hillsdale College. “And there’s no marketing and advertising costs. Because the federal government is ordering them to get it, ordering 78 million school kids to take that vaccine every year. What better product could you have?”

Stock prices for vaccine manufacturers fell precipitously almost immediately following news of the announcement on Thursday afternoon. As of 15 minutes before market close, Pfizer stock fell by 2.62%, and Moderna fell by 5.62%. Eli Lilly’s stock price fell by 3.15%.

Before becoming known as an outspoken vaccine skeptic, Kennedy was a prominent environmental lawyer with an illustrious career in combatting the use of poisonous toxins, including the 2007 DuPont case on behalf of rural West Virginian communities contaminated by zinc.

Most recently, he was involved in the case against Monsanto, the maker of herbicide RoundUp, for the use of the carcinogenic ingredient glyphosate.

Due to his unorthodox stance against vaccines, seed oils, and milk pasteurization, Kennedy is expected to have a difficult time gaining enough votes during the Senate confirmation process, even with a Republican majority in the chamber.

Sen. Bill Cassidy (R-LA), the first medical doctor since 1933 to chair the Health, Education, Labor, and Pensions Committee, would control Kennedy’s nomination at the committee level.

“RFK Jr. has championed issues like healthy foods and the need for greater transparency in our public health infrastructure,” Cassidy said in a news statement. “I look forward to learning more about his other policy positions and how they will support a conservative, pro-American agenda.”

Even if Kennedy does not make it through the confirmation process, he likely will be an adviser on public health matters to the new Trump administration, including whoever is selected to be HHS secretary in his stead.

On Thursday, Democratic members of the House Oversight Committee took time from a hearing overviewing the lessons learned from the COVID-19 pandemic to argue that Kennedy would be disastrous for public health, particularly future pandemic preparedness.

“The fact that we’re considering bringing somebody on with no scientific or medical credentials, who’s falsely claimed for decades of vaccines caused autism, who has, quite frankly, said just outrageous comments about science and medicine that this person would come in to gut the NIH, I think is shameful,” Rep Robert Garcia of California said.