The company said that the pill reduced combined hospitalizations and deaths by about 89 percent among high-risk adults when taken shortly after initial COVID-19 symptoms.
Separate laboratory testing shows the drug retains its potency against the Omicron variant, the company announced, as many experts had predicted. Pfizer tested the antiviral drug against a man-made version of a key protein that Omicron uses to reproduce itself, reported India Today.
The updates come as Covid-19 cases, deaths and hospitalization are all rising again and the US hovers around 800,000 pandemic deaths. The latest surge, driven by the delta variant, is accelerating due to colder weather and more indoor gatherings, even as health officials brace for the impact of the emerging Omicron mutant.
The Food and Drug Administration is expected to soon rule on whether to authorise Pfizer's pill and a competing pill from Merck, which was submitted to regulators several weeks earlier. If granted, the pills would be the first Covid-19 treatments that Americans could pick up at a pharmacy and take at home.
Pfizer's data could help reassure regulators of its drug's benefit after Merck disclosed smaller-than-expected benefits for its drug in final testing.
Merck, however, last month said that its pill reduced hospitalizations and deaths by 30 percent in high-risk adults. The drugs have been studied by both the companies in unvaccinated adults who face the gravest risks from COVID-19 due to older age or health problems such as asthma or obesity.
The pill is also studied in lower-risk adults but reported mixed data for that group, Pfizer said.
Pfizer said that in interim result, its drug failed to meet its main study goal: sustained relief from Covid-19 for four days during or after treatment, as reported by patients. But the drug did achieve a second goal by reducing hospitalisations by about 70 per cent among that group, which included otherwise healthy unvaccinated adults and vaccinated adults with one or more health issues. Less than 1 per cent of patients who got the drug were hospitalised, compared with 2.4 per cent of patients who got a dummy pill.