What happened

Investors sold off shares of several coronavirus vaccine-related stocks on Friday as lawmakers ramp up pressure on drugmakers.

By the close of trading, shares of Vaxart (NASDAQ:VXRT), Inovio Pharmaceuticals (NASDAQ:INO), BioNTech (NASDAQ:BNTX), and Moderna (NASDAQ:MRNA) were down 11.3%, 10.9%, 4.9%, and 2.8%, respectively.

So what

In hearings that took place this week, lawmakers grilled drug companies on their pricing plans for their potential vaccines, with some going so far as to ask executives at companies including Moderna, Johnson & Johnson, and AstraZeneca if they would supply their vaccines at cost. "We will not sell it at cost, no," Moderna President Dr. Stephen Hoge said during a congressional hearing on Tuesday. 

A person points to a digital stock chart that rises, then falls.

Investors took some profits in COVID-19 vaccine stocks on Friday. Image source: Getty Images.

While executives from other pharmaceutical companies also largely declined to agree to provide their potential vaccines at prices that would provide them with zero profits, the pressure from Congress to do so appears to be rising.  

Now what 

Even shares of BioNTech -- which, along with its partner Pfizer, locked up a nearly $2 billion order for its COVID-19 vaccine candidate from the U.S. government on Wednesday -- saw its shares fall. Investors could be growing concerned that future deals may be negotiated more fiercely, and potentially at prices that could make profits difficult to come by.

This recent political pressure should serve as a reminder to investors: To successfully invest in vaccine makers, you'll need to determine not just which experimental COVID-19 vaccines will gain regulatory approval, but also whether the prices they can be sold at justify their company's stock valuations. Neither task is particularly easy.