• The forced resignation of FDA vaccine regulator Peter Marks has, in part, sparked anxiety in Big Pharma investors, as shares in Moderna and Novavax slide. Marks’ departure comes amid a sweeping overhaul of the Department of Health and Human Services, helmed by vaccine skeptic Robert F. Kennedy Jr.

Key personnel changes within federal public-health agencies have appeared to shake investor confidence in vaccine makers. Shares of Moderna and Novavax plunged Monday following the announcement Friday that key Food and Drug Administration official Peter Marks was stepping down from his position.

The share price of Moderna plummeted more than 12% since the personnel change as of Monday afternoon, while Novavax fell about 7%. 

Marks, head of the FDA’s Center for Biologics Evaluation and Research, was a key individual in regulating and approving vaccines and other treatments, such as gene therapies. During President Donald Trump’s first administration, Marks was credited for coining the name and concept of Operation Warp Speed, the initiative to expedite the development of Covid vaccines.

The regulator’s departure comes amid sweeping cuts in the Department of Health and Human Services, which include the elimination of 10,000 positions across 28 divisions. The HHS is currently helmed by Robert F. Kennedy Jr., who has previously espoused erroneous information about vaccines. Last week, the Senate confirmed Jay Bhattacharya, who opposed Covid vaccine mandates and lockdowns, as head of the National Institutes of Health.

Kennedy reportedly gave Marks the option of either resigning or being fired, an anonymous former FDA official told the Associated Press. Marks cited Kennedy’s spread of vaccine misinformation as one of the reasons for his resignation.

“I was willing to work to address the Secretary’s concerns regarding vaccine safety and transparency,” Marks said in his letter of resignation. “However it has become clear that truth and transparency are not desired by the Secretary, but rather he wishes subservient confirmation of his misinformation and lies.”

Big Pharma stocks responded similarly when Trump announced Kennedy as his pick to lead in November. Vaccine makers lost $8 billion in market capitalization overnight.

Moderna and the FDA did not respond to Fortune’s requests for comment. Novavax declined to comment.

Headwinds for Big Pharma

The massive overhaul within the HHS, particularly in the FDA, are a likely headache for pharmacy companies looking not only for vaccine approval, but for development, according to Myles Minter, a healthcare analyst at William Blair. Marks’ resignation signals to vaccine developers that the HHS has grown less friendly to vaccination efforts.

“This is a line in the sand that there could be some regulatory uncertainty for additional vaccines coming through the pipe,” Minter told Fortune. “And they are going to be incredibly important for Moderna.”

Shortly after Trump’s election victory, Moderna CEO Stéphane Bancel said the company would work with the administration using “facts and data.” Continued efforts by the Trump administration to divest in vaccine funding and spread misinformation could fracture that relationship, according to Minter.

The Trump administration plans to eliminate $28 billion in global-health funding, according to a leaked document viewed by Bloomberg and the New York Times. Those efforts include the 5,341 projects, such as HIV vaccine development, and funding to vaccine alliance Gavi. The Centers for Disease Control and Prevention, which HHS oversees, will conduct a large-scale study to look at the connection between vaccines and autism, which has been thoroughly debunked.

“It becomes increasingly difficult for vaccine developers to interact with an administration that keeps appointing people that are clear skeptics,” Minter said. “It has been said and viewed as a potential headwind there, despite the fact that they are open to working with whatever administration is put in place.”

This story was originally featured on Fortune.com