What happened

Top coronavirus stock BioNTech (BNTX 0.29%) was also tops with investors on Thursday. The Germany-based biotech's shares trounced the S&P 500 by closing the day more than 4% higher, thanks to some positive -- if expected -- news on the regulatory front.

So what

Comirnaty, the coronavirus vaccine developed by BioNTech in partnership with U.S. pharmaceutical sector giant Pfizer (PFE 0.91%), was granted Emergency Use Authorization as a booster by the Food and Drug Administration Wednesday night.

Person receiving an injection.

Image source: Getty Images.

The vaccine is currently the only one fully approved by the regulator to prevent COVID-19. Two other vaccines, from biotech Moderna and Johnson & Johnson's Janssen, are in circulation under EUAs.

The Comirnaty booster's EUA covers people 65 years of age and older. It also applies to individuals age 18 to 64 with either high risk of severe COVID-19, or, as the FDA wrote in an official press release on the matter, "whose frequent institutional or occupational exposure to SARS-CoV-2 puts them at high risk of serious complications" from the disease.

In a statement, BioNTech CEO Uğur Şahin said the company would "continue to monitor new SARS-CoV-2 strains, to be prepared for potential emerging escape variants."

Now what

BioNTech and Pfizer added that they are continuing to supply the vaccine under their current arrangement with the U.S. government, which runs through next April. According to the companies, this arrangement includes "sufficient volume for boosters."

The booster shots are likely not going to affect the financial projections for either company; however, the approval will bolster Comirnaty's status as the leading coronavirus vaccine administered in this country.