Robert F. Kennedy Jr., in his first national TV appearance as Health and Human Services Secretary under the Trump administration, questioned the effectiveness of Novavax's Covid vaccine during an interview with CBS News' chief medical correspondent, Dr. Jon LaPook. The interview, which cast doubt on the shot, sent shares of the Maryland-based biotech firm crashing on Thursday.

RFK Jr. told LaPook that Novavax's shot targets just one piece of the virus, an approach he said has "never worked" for respiratory illnesses:

We're looking at that vaccine, and it is a single-antigen vaccine. And, for respiratory illnesses, the single-antigen vaccines have never worked and we're actually shifting our priorities to multiple-antigen vaccines. And NIH is already working on a number of those.

RFK Jr.'s comments sent Novavax shares into a tailspin, plunging 24% during late-morning trading in New York. The stock has already suffered steep losses in recent years, falling back to pre-pandemic lows after the pandemic ended.

"Novavax's shot is already on the market under a conditional approval. It's awaiting from the Food and Drug Administration a full approval that was expected April 1," Bloomberg noted.

In recent weeks, Wall Street analysts have raised concerns about Peter Marks' abrupt resignation. Marks was a top FDA regulator and pro-vaxxer. 

Analysts—including BMO Capital Markets' Evan David Seigerman—viewed Marks' departure as a "significant negative" for the biotech and biopharma sectors. 

The share of SPDR S&P Biotech ETF (XBI) is down about 34% since Trump won the presidential election and Wall Street's fear that RFK Jr. would push through major reforms at HHS that would hurt the vaccine industrial industry

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