Can Pfizer’s pill get to those who need it?

Limited supply, the need for quick diagnoses may complicate prescriptions

An antiviral drug being hailed for its potential role in the treatment of COVID-19 is now available in Ontario, but doctors warn it comes with significant challenges including low supply.

Around 30,000 courses of Pfizer’s oral antiviral treatment Paxlovid arrived in Canada last week, with 11,000 of those distributed to Ontario, noted Dr. Andrew Morris, a professor of infectious diseases at the University of Toronto and a member of the provincial science table.

As Omicron cases continue to rise, a treatment like Paxlovid could play a key role in preventing severe illness, hospitalization and death, especially for the most vulnerable. Pfizer said in December the oral treatment showed almost 90 per cent efficacy in preventing hospitalizations and deaths in high-risk patients.

Patients undergoing treatment take two tablets of nirmatrelvir — the active ingredient which stops the virus from replicating — along with one tablet of another antiviral called ritonavir twice a day for five days. The treatment is expected to be effective against the Omicron variant, according to Pfizer.

But because of high demand and limited supply, there may be significant caveats to using the treatment effectively, Morris warned.

“It’s not a panacea,” Morris said. “Many patients who would be potentially eligible for treatment probably won’t end up getting it and part of this reason is supply.”

“The drug works and the data is very good … but there’s a bunch of caveats and the complexity of getting it to as many people as possible. It’s not going to spell the end of the pandemic.”

Health Canada’s authorization of Paxlovid is for adults who are at high risk of serious illness from COVID with mild to moderate symptoms and are within five days of infection. The Public Health Agency of Canada has asked provinces to prioritize individuals at highest risk for severe illness and hospitalization, as well as make greater supply available in rural and remote communities where access to health care is limited.

Another barrier is access — tied to continuing delays in COVID testing. The treatment must be administered within five days of symptom onset and tests are difficult to find.

“In Ontario there’s a waiting list to get tested and it takes at least 24 hours before you can get a testing spot … and then those results might come back a day or two later,” Morris said.

Shortages of critical drugs to treat COVID-19 patients have escalated amid a surge of cases and the highly transmissible Omicron variant.

Dwindling stock in Ontario has forced some physicians to choose which patients receive potentially life-saving care, while others don’t have access to the medicine at all.

“We have a shortage of pretty well every drug except for dexamethasone,” Morris said, adding that drugs including tocilizumab and baricitinib given to critically ill COVID patients are currently in short supply. Sotrovimab, a monoclonal antibody treatment, is also running low.

Alongside supply issues, another caveat with Paxlovid regards possible complications with drug interactions, explained Dr. Allan Grill, chief of family medicine at Markham Stouffville Hospital. Some drugs often taken by highrisk patients, including heart medications and blood thinners, could be affected by the antiviral treatment, which means those receiving it will have to monitor interactions with the help of their doctors.

While Grill said he is optimistic about the arrival of the new treatment, he stressed that vaccination should still be the priority to protect people because of these challenges.

“I’m always optimistic whenever we can add tools to our current tool box to protect patients against COVID-19,” Grill said. “But people need to understand that it’s not that straightforward. Prevention is better than treatment, but obviously whatever treatment we have that can benefit people who are eligible, of course I support.”

It is hard to determine how long the first shipment will last as demand will be driven by the public, Morris said.

While the rate of hospitalizations due to COVID appears to be slowing, “it’s very dynamic. For example, schools reopening may change things so it’s difficult to know if demand will go up or down.”

Currently, provinces and territories will get the final say about who will receive the treatment. Federal Health Minister Jean-Yves Duclos previously said the treatment will be distributed to the provinces and territories on a per-capita basis, while an additional 120,000 Paxlovid courses are set to arrive by the end of March.

But this method of distribution fails to address inequities faced by vulnerable and remote communities including Indigenous peoples throughout Canada, pointed out Dr. Anna Banerji, a pediatrician and U of T professor.

“For example, in remote Indigenous communities there are higher rates of comorbidities such as kidney disease, hypertension and diabetes … there is more overcrowding in houses which makes isolation difficult,” she said. “This drug could be life-changing but the guidelines need to be reflective of this need.”

Some drugs often taken by high-risk patients, including heart medications and blood thinners, could be affected by the antiviral treatment