Will Canada approve a first-dose-first strategy now that AstraZeneca has been approved?

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This week, buoyed by the apparent success of a “first dose first” vaccine rollout, U.K. Prime Minister Boris Johnson unveiled a plan to slowly unshackle England from COVID restrictions by the end of June.

The U.K.’s controversial strategy to space vaccine doses up to three months apart, rather than the originally approved three to four weeks, in order to give as many people at least one shot sooner could see every British adult offered a first dose of a COVID vaccine by the end of July — months sooner than Canada.

Now, an independent federal expert advisory panel is once again mulling dosing gaps in Canada: How far can you push it to give more people shots?

“We are already at six weeks,” Dr. Caroline Quach, chair of the National Advisory Committee on Immunization, said in a brief email exchange with the National Post before two days of meetings this week. “(The panel) will see what else can be recommended.”

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It’s clearly advantageous if we can get most of the population vaccinated

It’s unlikely the group would endorse the U.K. plan of a 12-week interlude between doses. Some observers think they won’t blink at nine weeks but that it’s not clear where they will stop.

The panel’s deliberations come as a third vaccine — this one from Oxford University and pharma giant AstraZeneca — was officially authorized for use in Canada Friday. Canada’s pre-ordered, 20 million doses are scheduled to arrive in the second and third quarter of the year.

Except for the Johnson and Johnson vaccine, which is a single-shot jab, a second booster dose is vital to lock in and extend immunity for all the COVID vaccines. On this, everyone agrees. No one is saying one-dose-and-done.

But the debate over delaying those second, booster doses has been polarizing and emotional, with opponents warning it’s not known how long immunity persists after the first dose and that “sub optimal” vaccination risks giving rise to more super-infectious, mutated variants.

Others argue immunity doesn’t wane that fast between shots and let’s not leave people unprotected and risk more deaths and economic casualties.

While the data are still early, “the indications are that there’s a good level of protection after just one dose,” Canada’s deputy chief public health officer, Dr. Howard Njoo, told reporters last week.

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Ottawa has said it expects to receive a combined 29 million doses of the Pfizer and Moderna vaccines by the end of June, enough to fully vaccinate 14.5 million people. But immunizing 20 million people — if logistical and technical glitches can be overcome — by spreading out the shots could help break the back of the epidemic sooner. The vaccines currently aren’t approved for children under 16.

“It’s clearly advantageous if we can get most of the population vaccinated” with a first shot by early summer, said Aidan Hollis, a professor of economics at the University of Calgary who specializes in pharmaceutical markets.

“The U.K. has been stretching out the timing of doses for quite a while now,” he said, stressing he’s not trying to claim expertise in immunology or vaccinology. “There’s an opportunity to learn from what’s happening in other jurisdictions.”

The original dosing schedules for Canada’s two approved vaccines — Pfizer-BioNTech and Moderna — require two doses, 21 days (Pfizer) and 28 days (Moderna) apart.

In January, amidst a lethargic vaccine rollout, Quach’s expert vaccine advisory panel came up with a compromise: It said that spacing shots out to a maximum of six weeks seemed safe and reasonable, though the original schedule was still preferred.

“In our usual Canadian fashion, provinces responded in different ways,” said Dr. David Naylor, co-chair of the federal government’s COVID-19 Immunity Task Force. Ontario opted for 42 days. Quebec allowed 90 days between jabs — a scheme that appears to be working.

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According to preliminary, unpublished data, the Pfizer-BioNTech and Moderna vaccines have been roughly 80 per cent effective in preventing disease after the first dose, Quebec public health officials said this week.

Meanwhile, a massive real-world trial out of Israel appearing in this week’s New England Journal of Medicine, found a single dose of the Pfizer shot was 62 per cent effective against preventing severe illness, at 14 days through 20 after the first dose, 74 per cent effective against COVID-related hospitalizations and 72 per cent effective at preventing deaths.

A second study, a pre-print published by the Lancet, found that the Oxford/AstraZeneca vaccine provided 76 per cent protection after the first dose. Protection didn’t wane during the three-month gap between needles — there was some evidence it actually builds — and there was a hint that a longer gap (three months) between shots is better than a shorter (six week) one.

The data “provide reassurance that if the AstraZeneca vaccine comes into wide use in Canada we have many weeks of flexibility before a second dose of it is given,” Naylor said, though he stressed the need for continuing vigilance about vulnerable groups, including frail seniors and the immune compromised.

Naylor hopes they extend the window. The real world evidence is no longer lacking, he said. “The math has been obvious. Getting more first doses into more people faster will save lives.”

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But while all available vaccines produce “impressive” short-term immunity with a single shot, “how they do so in the intermediate and long term is less known, verging on unknown, especially in the sense of forming lasting immunological ‘memory,’” said Amir Attaran, a University of Ottawa health law professor who has a PhD in immunology.

“Further, what is going to happen if you vaccinate once, postpone the second shot, and then come back with a different vaccine later because additional doses of the first vaccine are not available? Can you mix and match vaccines?  Are some combinations better or worse than others?  We have zero data,” Attaran said.

As of Thursday, 3.1 per cent of Canada’s population had received at least one dose of a COVID-19 vaccine, versus 27 per cent of the U.K.’s population.

National Post