An experimental antiviral pill from Pfizer reduced Covid patients' risk of death and hospitalization by 89% in a large study.

An experimental antiviral pill developed by Pfizer reduced the risk of death and hospitalization by 89% in patients who were newly diagnosed with Covid-19 in a large study. 

The Pfizer medicine, known by the code name PF-07321332 or simply ’332 (brand name Paxlovid), reduced hospitalization by 89% compared to placebo when given within three days of symptom onset. The medicine also reduced the chance that patients would die. There were 7 deaths out of 385 patients in the placebo group, and none in the 389-patient group that received the medicines.

The study, which was originally set to enroll 3,000 patients who would receive either placebo or the combination of ’332 and ritonavir, would stop at different timepoints depending on how effective the medicines proved to be.

An outside data safety monitoring board stopped the study early when 774 patients had been treated for 28 days. In that time frame, 27 (7%) of those on placebo were hospitalized or died compared to 3 who received ’332 and ritonavir. That translates into an 89% reduction between the groups. The study also allowed patients to start taking the treatment (or placebo) within five days after symptoms appeared, not three. In that group of 1,219, there were 41 patients who were hospitalized or died in the placebo group compared to 6 who received the medicines, an 85% reduction.

Pfizer results have not been submitted to regulators yet, however Pfizer said it plans to make the drug available using a “tiered pricing approach” based on the income level of each country. 

Pfizer has two more studies of the drug ongoing. This study was in patients with risk factors for severe Covid who were unvaccinated. A second study is testing the drug in lower-risk patients and those who have been vaccinated, potentially making it an option for treating breakthrough infections. A third will test whether the drug can prevent infection in people who are likely to be exposed to the virus.