Ulrich Baumgarten/Getty Images/File
Original vaccination vials from Moderna, Comirnaty (Pfizer/BioNTech) and Nuvaxovid (Novavax) on April 27, 2022.
New York CNN  — 

Shares of prominent vaccine makers plunged Thursday after President-elect Donald Trump announced his pick of Robert F. Kennedy Jr. to be the next secretary of the Department of Health and Human Services.

An hour before the market closed Thursday, as news reports of Trump’s choice began trickling out, Covid-19 vaccine maker Moderna dipped as much as 6%, and Pfizer fell almost 2%. Novavax, which created a protein-based Covid-19 vaccine, fell almost 6%.

Kennedy has been one of the country’s most prominent anti-vaccine conspiracy theorists for years and has frequently spread falsehoods about the safety and efficacy of vaccines. Last week, Kennedy said he would “immediately” begin studying vaccine safety and efficacy but promised to not “take vaccines away from anybody.”

Other vaccine-related companies also felt the fallout. German company BioNTech closed 7% lower, and British GSK fell 2%. US vaccine companies have already been struggling, thanks to lessened demand since the peak of the pandemic. Over the past year, Pfizer stock has dipped 11%, and Moderna stock has plunged 46%.

While Pfizer revenue and profits soared during the peak of the pandemic – generating nearly $57 billion in combined sales in 2022, thanks largely to its Comirnaty Covid-19 vaccine and Paxlovid antiviral pill – the boom subsided by early 2023, and the company slashed its expectations for Covid-related sales. By then, public health agencies already had an effective stockpile of vaccines to treat patients.

After Trump made the announcement official, the stocks fell further.

“The Safety and Health of all Americans is the most important role of any Administration, and HHS will play a big role in helping ensure that everybody will be protected from harmful chemicals, pollutants, pesticides, pharmaceutical products, and food additives that have contributed to the overwhelming Health Crisis in this Country,” Trump said in a post on X.

CNN’s Kaitlan Collins, Kristen Holmes and Aaron Pellish contributed to this report.