An (Interim) One-Dose Vaccine Strategy?

"We're in the middle of a pandemic and we're starting to get needles into people, and there are challenges with that. They're going full-steam trying to supply vaccine, but there are shortages right now."

"I think the fact that we're in the real world -- and not a perfect world where you have everything available to you, with two doses lined up for everybody -- I think the case gets stronger [for a single dose], given this fairly good protection after the prime [shot]." 

"You could make a case for vaccinating twice as many people with the prime, and get to the boost when you can, and quickly get it to those who need it most. I think there's some merit to that."

Earl Brown, professor emeritus, Faculty of Medicine, University of Ottawa

"Up to now in the province, we've been taking a precautionary approach. So, because the supply was not stable, we were holding back the second dose to make sure everyone who got the first dose would get the second dose at the 21-day mark."

"Now, we have information from the federal government that the supply of Pfizer vaccines is much more stable -- we can expect it on certain days and [in] certain amounts. So we have informed the hospitals that are involved and the public health units that they should give out more of the first dose, so that more people can be more protected, and also assure that more people do get the second dose at the right time."

"[While there were promising early signals in the efficacy data after a single dose] we don't know for how long that [immunity] would last."

"And the product monograph and the information from the trials that were done by Moderna does say that you should have a second dose after 28 days. So, I think that's something we'll have to look into further with Health Canada."

Dr.Barbara Yaffe, associate chief medical officer of health, Ontario

Care home workers get the Pfizer-BioNTech COVID-19 vaccine at a clinic in St. Michael’s Hospital in Toront. (Evan Mitsui/CBC)

In the face of current scarcity of various pharmaceutical manufacturers' anti-COVID vaccines, it sounds like a good idea, a compromise between a still-scarce product and the numbers of people awaiting inoculation against a dread virus causing a disease with a high mortality rate among the aged in any human population. A recommendation largely based on reports through product trials of a high degree of efficacy for the initial dose of a protocol recommending two shots; the first and a follow-up to complete the protocol as opposed to some experts now hypothesizing a greater volume of inoculations are achievable in suspending the second dose in favour of widening the one-dose pool of recipients.

Co-authored by Harvard epidemiologist Michael Mina, an opinion piece published recently in the New York Times cites studies indicating "significant protection" gained against COVID-19, "even without a second shot". The very data collected from initial clinical trials indicate a 92.5 percent efficacy for the Moderna vaccine in the two weeks following the application of the first dose. In the case of the Pfizer-BioNTech vaccine, that efficacy rate is 82.5 efficiency, both extremely high numbers of success in efficacy.

"If studies prove that's true, it could be a game-changer" the authors wrote with a news headline asking "Can we do twice as many vaccinations as we thought?" The second sober thought is recollecting that both of these manufacturers has a requirement for a second "booster" dose to be administered following 21 days for the Pfizer vaccine, and 28 days for the Moderna vaccine, after the inoculation of the first dose has been completed.

A nurse works in an ICU. Photo by Shannon Stapleton /REUTERS

 

When the Province of Ontario -- after receipt of its share of the first vaccines delivered to Canada by Pfizer -- decided to hold back vaccines to account for second doses rather than use the entire initial shipment in covering a larger number of people, covering the first selected for the vaccination program based on the vulnerability of exposure, capturing those elderly patients living in long-term care homes, their attendants, hospital health-care workers and finally populations over the age of 80, that approach reflected the pharmaceutical companies' trial findings for the achievement of the greatest efficacy.

It was a decision, however, that was reversed on the basis of a convincing argument that it was a needless precaution, when the federal government assured the government of Ontario that sufficient incoming supplies would fill the gap of failing to set aside half of the doses to complete the cycle, so the stage was set to use the entire dose allocation for single, initial vaccination shots among the identified group of vulnerables. Dr.Yaffe, in her role as a spokesperson for the province's health authority that while promising early signals in efficacy data following a single dose, alludes to the uncertainty that remains.

Yet, despite the clinical trials demonstrating that a single dose provided extraordinary efficacy rates and a vast data pool exists to indicate the immunity will have month-lasting effects, the doubt respecting those data represents cause for caution. 

Jo-Anne Miner, Personal Support Worker at St. Patrick’s Home, was the first to receive the vaccine! “This is will help create a safe space for me, my colleagues, and the residents.”

"The question is, how much are you willing to gamble on things you don't know about? [While clinical trials have demonstrated] extraordinary [efficacy rates after a single dose, and there are volumes of data showing the immunity will last for months] we don't know if that immunity would have lasted past the 28 days, when the second dose was given. And we don't know that because the second dose was given [in those trials]."

"If you go for a one-dose approach, would that technically be an 'off-label' application of this medication? And if that's the case, is that a responsible thing to do, given what's at stake here?'

"We have this uphill battle to convince people the vaccine is safe and effective, given the rapidity of its development. [A major tool for that] public buy-in [is the] remarkably rigorous [clinical trial data made public by Health Canada.]"

"That data was the basis by which Health Canada rendered its decision [to authorize], and if suddenly we are deviating from the [two-dose] protocols described in the clinical trial, that threatens public buy-in."

"It's worth exploring at the scientific level for the next few months, but in the interim it strikes me as an irresponsible thing to do, when you just don't know, and the stakes are so high."

Dr.Raywat Deonandan, epidemiologist, associate professor, Faculty of Health Sciences, University of Ottawa