A trial of Pfizer Inc's experimental antiviral pill for Covid-19 was stopped early after the drug was shown to cut by 89 percent the chances of hospitalisation or death for adults at risk of developing severe disease, the company said on Friday.

The results appear to surpass those seen with Merck & Co Inc's pill, molnupiravir, which was shown last month to halve the likelihood of dying or being hospitalized for Covid-19 patients also at high risk of serious illness.

Full trial data is...