Once touted as a COVID-19 'game changer,' Paxlovid is now a question mark for clinicians

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If you catch the virus behind COVID-19 and you're at a high risk of serious illness, there's one major tool in a physician's arsenal to keep you out of hospital: Paxlovid.

Pfizer's antiviral drug was hailed as life-saving when it burst onto the scene midway through the pandemic. Clinical trials, conducted on people who'd never been vaccinated, showed it protected those vulnerable individuals from becoming dangerously sick, with a nearly 90 per cent reduction in the risk of hospitalization and death.

But many clinicians agree the COVID landscape has shifted dramatically since early January 2022 when the drug was approved for use in Canada. Now, the vast majority of Canadians have more protection from serious illness through prior vaccination, infection or both.

So where does Paxlovid fit into the treatment picture now? The answer remains murky.

Some doctors warn about patchwork, muddled guidance over who should be eligible for the drug, while others point to a lack of up-to-date research, meaning it's unclear whether Paxlovid is effective in a population that's been so heavily exposed to this virus. 

At the same time, SARS-CoV-2 is still circulating widely, and remains linked to thousands of hospitalizations and dozens of deaths on a weekly basis. Meanwhile, tens of thousands of treatment packs are sitting unused in provincial stockpiles, raising concerns over whether the people who could still benefit from the treatment are even able to access it.

"[Paxlovid] was, at the time, hailed as a game changer. This was clearly demonstrated with high-quality evidence… and I think it was very appropriate to procure a significant amount of the drug for our country," said Dr. Nathan Stall, a geriatrician with Sinai Health System in Toronto.

"The thing is, we've seen multiple times [that] the pandemic changes — and it changes very quickly. And so I don't think we should be prescribing drugs because we have supply; we should be prescribing drugs to patients who need it."

Nirmatrelvir/ritonavir, sold under the brand name Paxlovid, is an oral combination medication that's taken for five days and stops the virus from multiplying inside someone's body.

In Canada, it's approved for use in adults "who have a high risk of getting severe COVID-19, including hospitalization or death."

But the definition of who exactly is deemed "high risk" — and therefore eligible to get the drug — varies widely from province to province. Provincial public health teams base eligibility on a mix of factors: age, vaccination status, elapsed time since their last dose, and whether they're immunocompromised or have other serious health conditions.

Multiple jurisdictions, including Ontario, say vaccinated adults as young as 60 are eligible for a prescription. B.C. doesn't offer it to anyone under 70 if they're vaccinated against COVID. Meanwhile Nova Scotia's public referral form, last updated in October 2023, paints a picture of how complex those layered factors can get, with numerous criteria dictating whether or not someone should get the drug. 

"Whenever you see a real mess of guidelines, that means that the data is crummy," said Dr. Lynora Saxinger, an infectious diseases specialist with the University of Alberta.