New data suggests Canada's 'gamble' on delaying, mixing and matching COVID-19 vaccines paid off
Early data suggests strong protection against delta, no evidence for boosters in the general population yet...
Quebec data backs up findings from B.C.
In Quebec, thousands of kilometres away and with a different population, demographic makeup and early vaccine rollout approach — the results of a twin study that will be published alongside the B.C. data were astonishingly similar.
Of the 181 people who died from COVID-19 from May 30 to Sept. 11 in Quebec, just three were fully vaccinated. Researchers say that corresponds to a vaccine effectiveness against death upwards of 97 per cent based on a population analysis of nearly 1.3 million people.
Similar to the B.C. data, the Quebec research also showed more than 92 per cent protection from hospitalizations — with Pfizer, Moderna or AstraZeneca vaccines — against all circulating coronavirus variants of concern in Canada at that time, including delta...
The NACI recommendation in March to delay second doses of all three COVID-19 vaccines by up to four months was not without controversy at the time, and no doubt led to confusion among many Canadians about whether they were adequately protected.
Canada's Chief Science Adviser Mona Nemer said in early March that the strategy amounted to a "population level experiment," while at the same time health officials tried to reassure the public that the approach was safe and effective.
Deepta Bhattacharya, an immunologist at the University of Arizona who was not involved in the study, says the results are "very encouraging" and provide evidence of "improved real world protection" from delaying second doses.
But he admits even he was initially skeptical.
"I was uneasy about it in large part because I just wasn't sure how well the protection would hold up in the interim," he said. "Obviously it turned out well … but it was risky, and that gamble paid off."
Bhattacharya says the Canadian data now provides real world evidence that vaccinated people produce more antibodies if their second shot is delayed, and the quality of those antibodies may actually improve — which could explain the better protection against delta.
"What I'm really wondering now going forward is whether the recommendations are going to fundamentally change as to when we should get that second shot," he said, referring to other countries around the world. "I wish I'd gotten mine later now in retrospect."
Keeping 'eye on the prize' means avoiding hospitalization
The data also has implications on whether average Canadians need booster shots, particularly given that emerging real world data in other countries like the U.S., Israel and Qatar show evidence of waning immunity that has prompted the rollout of third doses.
But experts caution that while countries reporting diminished vaccine effectiveness against COVID-19 infection may be making headlines, the more important factor is that the studies largely show the vaccines have prolonged protection against severe COVID-19 — meaning hospitalization and death.
"We really should keep our eyes on the prize, which is preserving healthcare system capacity and preventing unnecessary suffering," said Skowronski. "We're not going to prevent every case of COVID-19. Our goal was never to prevent the sniffles. Our goal was to prevent serious outcomes."
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wrbtrader
Early data suggests strong protection against delta, no evidence for boosters in the general population yet...
Quebec data backs up findings from B.C.
In Quebec, thousands of kilometres away and with a different population, demographic makeup and early vaccine rollout approach — the results of a twin study that will be published alongside the B.C. data were astonishingly similar.
Of the 181 people who died from COVID-19 from May 30 to Sept. 11 in Quebec, just three were fully vaccinated. Researchers say that corresponds to a vaccine effectiveness against death upwards of 97 per cent based on a population analysis of nearly 1.3 million people.
Similar to the B.C. data, the Quebec research also showed more than 92 per cent protection from hospitalizations — with Pfizer, Moderna or AstraZeneca vaccines — against all circulating coronavirus variants of concern in Canada at that time, including delta...
The NACI recommendation in March to delay second doses of all three COVID-19 vaccines by up to four months was not without controversy at the time, and no doubt led to confusion among many Canadians about whether they were adequately protected.
Canada's Chief Science Adviser Mona Nemer said in early March that the strategy amounted to a "population level experiment," while at the same time health officials tried to reassure the public that the approach was safe and effective.
Deepta Bhattacharya, an immunologist at the University of Arizona who was not involved in the study, says the results are "very encouraging" and provide evidence of "improved real world protection" from delaying second doses.
But he admits even he was initially skeptical.
"I was uneasy about it in large part because I just wasn't sure how well the protection would hold up in the interim," he said. "Obviously it turned out well … but it was risky, and that gamble paid off."
Bhattacharya says the Canadian data now provides real world evidence that vaccinated people produce more antibodies if their second shot is delayed, and the quality of those antibodies may actually improve — which could explain the better protection against delta.
"What I'm really wondering now going forward is whether the recommendations are going to fundamentally change as to when we should get that second shot," he said, referring to other countries around the world. "I wish I'd gotten mine later now in retrospect."
Keeping 'eye on the prize' means avoiding hospitalization
The data also has implications on whether average Canadians need booster shots, particularly given that emerging real world data in other countries like the U.S., Israel and Qatar show evidence of waning immunity that has prompted the rollout of third doses.
But experts caution that while countries reporting diminished vaccine effectiveness against COVID-19 infection may be making headlines, the more important factor is that the studies largely show the vaccines have prolonged protection against severe COVID-19 — meaning hospitalization and death.
"We really should keep our eyes on the prize, which is preserving healthcare system capacity and preventing unnecessary suffering," said Skowronski. "We're not going to prevent every case of COVID-19. Our goal was never to prevent the sniffles. Our goal was to prevent serious outcomes."
----------
wrbtrader
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