What happened

Top coronavirus stock BioNTech (BNTX 0.06%) closed 5.5% lower on Tuesday. This was an unusual move for a company that has been wildly successful and, therefore, extremely popular on the exchange. But some potentially alarming coronavirus news coming from Europe seems to be dampening sentiment on the company.

So what

A new, faster-spreading variant of the coronavirus has been detected in the U.K. following a surge in cases in its Southeast. This has stoked dark fears of a strain able to resist the current crop of vaccines being approved, which happens to be led by BioNTech and Pfizer's (PFE -0.75%) BNT162b2.

Healthcare workers prowling the hallway of a hospital.

Image source: Getty Images.

More worryingly, the Centers for Disease Control and Prevention said Tuesday that the variant could already be circulating within the U.S. Unlike our country, over 40 nations around the globe instituted a temporary ban on travel from the U.K.

The new strain has yet to be properly and fully evaluated, although the high-profile director of the government's National Institute of Allergy and Infectious Diseases, Dr. Anthony Fauci, has said that it does not appear to be relatively more virulent.

Now what

I think this latest fear is compounded by no small amount of profit-taking. After all, BioNTech stock has been a rocket ever since becoming a leader in the coronavirus vaccine race alongside Pfizer. So far, we don't know enough about the new strain to trade stock on it, and the biotech sector is only at the beginning of the mRNA vaccines and medicine revolution.