Pfizer is already making billions of vaccine shots, but may now have a new weapon against Covid.
An antiviral pill trialled by the U.S. drugmaker has been shown to cut the chances of hospitalization or death from Covid for the most at risk adults by 89%.
Pfizer made the announcement Friday (November 5).
The results appear to be even better than those seen with a pill from rival Merck.
Last month that was shown to halve the likelihood of dying or being hospitalized for patients also at high risk of serious illness.
Full trial data is not yet available from either company.
But Pfizer said it plans to submit interim results for its pill to U.S. regulators.
The firm's study involved just over 1,200 patients.
It looked at hospitalizations or deaths among people diagnosed with mild to moderate COVID.
The trialists also had at least one risk factor for developing severe disease.
The experiment found just 0.8% of those given the drug were hospitalized within three days of symptom onset.
None had died by 28 days after treatment.
That compared with seven deaths for patients given a placebo.
Pfizer did not detail side effects of the treatment.
But the drugmaker said about 20% of both treatment and placebo patients had adverse effects.
The treatment will have the brand name Paxlovid and is made up of three pills given twice daily.