Shares of vaccine companies fell on Tuesday after a Senate panel voted to advance Robert F. Kennedy Jr.’s nomination to lead the Department of Health and Human Services to the full chamber. 

The committee voted 14 to 13 to advance Kennedy in a party-line vote around 10:30 a.m. ET.

Moderna‘s stock fell about 6% and shares of BioNTech dropped nearly 2%. Shares of Novavax fell nearly 1%, while GSK‘s stock dropped slightly. Pfizer‘s stock fell more than 1%, even after the company reported fourth-quarter results that topped expectations. Their shares initially fell by larger margins following the Senate committee vote, then regained some ground.

Kennedy, 71, is a notorious vaccine skeptic, making false claims that they are linked to autism despite decades of studies that debunk that association. But Kennedy, during Senate confirmation hearings last week, contended that he is not “anti-vaccine.” 

Kennedy is also the founder of the nonprofit Children’s Health Defense, the most well-funded anti-vaccine organization in the U.S. In a government ethics agreement last month, he said he stopped serving as chairman or chief legal counsel for the organization as of December.

If confirmed by the Senate, Kennedy would oversee federal health agencies that regulate vaccines and other drugs. Some health policy experts have raised concerns about Kennedy using his new potential platform to spread anti-vaccine rhetoric and deter Americans from receiving recommended shots at a time when vaccination rates are already falling, especially among children.

During an industry conference in January, Pfizer CEO Albert Bourla said Kennedy’s anti-vaccine rhetoric is in “complete contradiction” with what the company, regulators and the medical and scientific community believe.