Pfizer testing oral pill for prevention of COVID

What to expect: The mid-to-late-stage study will test Pfizer's drug, PF-07321332, designed to block the activity of the main enzyme the coronavirus needs to multiply, per a Pfizer statement.

• This will be co-administered with a low dose of ritonavir, which is widely used in combination treatments for HIV infection.

For the record: Remdesivir, a drug investigated earlier to treat Ebola and other diseases, is to date the only antiviral approved in the U.S. for COVID-19.

What they're saying: Mikael Dolsten, chief scientific officer and president of Pfizer, said in a statement that the drug would complement the "impact that vaccines have had in helping quell infections."

• "If successful, we believe this therapy could help stop the virus early — before it has had a chance to replicate extensively — potentially preventing symptomatic disease in those who have been exposed and inhibiting the onset of infection in others," Dolsten added.