New research shows antiviral drug helps with COVID-19 recovery
April 23/2026
By Lisa Varano
This story was originally posted on Temerty Faculty of Medicine.
The results of two clinical trials show that Paxlovid, an oral antiviral drug, does not reduce hospital admissions or deaths in vaccinated adults at higher risk of severe COVID-19. However, the drug does help people recover a few days faster.
The research, led by U of T researchers also affiliated with the Upstream Lab at St. Michael’s Hospital, and researchers at Oxford University, was published in the New England Journal of Medicine.
The CanTreatCOVID study in Canada and the PANORAMIC study in the UK involved a total of more than 4,200 people.
“In terms of the use of Paxlovid, guidelines across Canada have evolved from its initial approval through the CanTreatCOVID study to today. They have progressively narrowed and I think that this evidence will further refine them,” says Andrew Pinto, who led the Canadian trial. Pinto is an associate professor at the Temerty Faculty of Medicine’s Department of Family and Community Medicine and the Dalla Lana School of Public Health.
Pinto is also the Director of the Upstream Lab, which is based at MAP Centre for Urban Health Solutions, and is part of St. Michael’s Hospital (Unity Health Toronto).
Andrew Pinto
In Ontario, the guidelines suggest that Paxlovid can be prescribed to treat mild-to-moderate COVID-19 in patients who are: 65 years of age and older, 18 years of age or older who are immunocompromised, or 18 to 64 years of age with at least one risk factor associated with more severe COVID-19 outcomes. For those not covered under the Ontario Public Drug Programs or private insurance, the cost could be about $1,400 out of pocket.
In January 2022, Health Canada authorized Paxlovid after initial study results revealed a reduced risk of hospitalization and death by nearly 90 per cent in unvaccinated high-risk patients. In contrast, the PANORAMIC trial (which took place from December 2021 to March 2024) and the CanTreatCOVID trial (which happened from January 2023 to September 2024) studied patients who were almost all vaccinated.
“In today’s highly vaccinated populations, the benefits of Paxlovid have fundamentally changed,” said Christopher Butler, of Oxford University, who led the UK trial. “While people feel better sooner, we found no reduction in the already low rate of hospitalizations or deaths. This provides essential high-quality evidence for optimal, cost-effective targeting of this treatment.”
University of Toronto assistant professor Benita Hosseini, professor Peter Selby, and associate professor Michelle Greiver also contributed to the research, as co-principal investigators of the CanTreatCOVID study. All are affiliated with the Temerty Faculty of Medicine’s Department of Family and Community Medicine, where Selby is vice-chair of research, and the Dalla Lana School of Public Health. Hosseini, Selby and Pinto are also affiliated with the Institute for Medical Science.
Both trials recruited vaccinated adults aged 50 and over, or younger adults with certain health conditions such as diabetes, heart disease, or a weakened immune system. All participants tested positive for COVID-19 and had symptoms for five days or less. Almost everyone (about 98 per cent) had already received at least one dose of a COVID-19 vaccine.
Interestingly, the studies revealed that Paxlovid did not reduce the chance of hospitalization or death from COVID-19 in those who were already vaccinated, but patients reported feeling better sooner and were more likely to stay recovered. In PANORAMIC, median recovery time was 14 days with Paxlovid compared to 21 days with usual care. CanTreatCOVID found recovery at 6 days versus 9 days.
CanTreatCOVID was one of the largest outpatient trials in Canada and has laid the groundwork for future research studies to be conducted in the community. It has been adapted into Upstream Lab’s new clinical trial called TreatResp, which launched in April 2026. TreatResp is designed to study treatments for respiratory infections, such as seasonal flu, and rapidly respond in the event of a future pandemic.
“For policymakers and funders, CanTreatCOVID demonstrates the value of having this type of research infrastructure ready to go so that we can study treatments for infections as they’re happening. In a new pandemic caused by a novel respiratory infection, our hope is TreatResp is fully up and running, and that it can be used to study treatments very quickly, both in terms of their efficacy and their cost-effectiveness,” says Pinto.
CanTreatCOVID involved researchers from across Canada, including McGill University, University of British Columbia, Simon Fraser University, University of Calgary, University of Manitoba, and Memorial University of Newfoundland.
CanTreatCOVID was funded by the Canadian Institutes of Health Research (CIHR) and Health Canada, and supported by the Public Health Agency of Canada.