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