With limited vaccine supply in Quebec, immunologist calls for second dose delay in Quebec


MONTREAL – As soon as the Government of Quebec announced that it would take the Pfizer COVID vaccines reserved for second doses and distribute them so that they can vaccinate more people in high-risk groups, Dr. Donald Vinh of the University McGill said the disinformation had started. spread.
“In fact, I heard people at my facility say that the second dose was canceled, and I said it was wrong. There is no plan from a government – by the provincial or federal governments to cancel the second dose, ”Vinh said.

Appointments for the booster injections, however, will be delayed beyond the three-week interval recommended by the manufacturer, due to the government’s decision.

It’s a policy change that has many people questioning the effectiveness of a single dose and whether the province is even allowed to take a different direction with the immunization schedule. Opinions abound.

The microbiologist and infectious disease specialist hopes to help dispel some of the confusion and adds that the government must “communicate clearly with the lay public … and address the concerns of people, especially the hesitant.”

This includes people like Tania Muhanna, who described herself as ‘vaccine hesitant’ when we met her just before Christmas, as she was considering whether or not to get vaccinated against COVID.

Now the patient attendant at a long-term care center in Dorval says she feels like the carpet under her has been ripped off.

Although she was never anti-vaccine and gets vaccinated every year, Muhanna was concerned about the COVID vaccine. She said many of her colleagues have done it too.

After asking McGill scientist Jonathan Jarry to answer some of her questions, Muhanna said she “just had to sit down with myself” and weigh the information.

She decided to take the plunge. Muhanna received her first dose of the Phizer COVID vaccine on December 27 and said she had not experienced any ill effects other than “a little tenderness in the arm” at the injection site.

“We focus so much on the possible negative side effects. I went there and was doing really great, ”Muhanna said in an interview with CTV News.

In the end, the Montreal frontline worker says she wondered if she was “ready to take this risk of not vaccinating and maybe getting something that can eventually kill you, or take something. which may or may not have side effects.

Muhanna concluded that getting the vaccine was “the most appropriate decision for me”, due to her job, her desire to protect her family and the fact that the number of cases “was skyrocketing again”.

But on January 8, Muhanna received an email from West Island health officials stating that “her appointment for the second dose of Pfizer vaccine had been canceled.”

The note she sent to CTV News went on to say that she would be contacted for a new appointment when a second dose was available, but that due to a new directive from the Department of Health, ” it is no longer required that this be done within 21 days of the first dose to ensure maximum protection. ”

“This is scandalous and unacceptable,” Muhanna said, as she had signed a consent form explaining the second dose protocol.


The decision to stop reserving second doses was due to the shortage of vaccine produced in the United States.

The federal government has announced that vaccine delivery will increase next month.

Deciding to use the second stored doses immediately follows “the principle of utilitarianism, meant to benefit as many people as possible,” Vinh said, as the virus rages and hospitals and health workers reach their point. a break.

The province of Ontario and some other countries are taking the same path as Quebec. New US President Joe Biden announced on Friday evening that his administration would also release nearly all available vaccine doses for the same reason.

But just because it’s a practical plan that responds to the urgency of the situation doesn’t mean there’s no scientific basis, said Vihn, who also sits on a group of COVID work for the federal government.

Both levels of government rely on the work of advisory committees made up of scientists, clinicians, lawyers and ethicists when making policy decisions like this.

The Quebec Immunization Committee reportedly reviewed the literature, the existing supply problem and COVID rates before recommending the approach.

“What we’re doing (in Quebec) is a bit out of the script – it’s true,” Vinh said.

But there is “a biological plausibility that a delay between the first and second dose beyond three to four weeks may actually elicit a better response or may have a neutral effect – will not make any difference, at six to eight weeks. “.

He overheard the serious concerns expressed by some members of the Montreal medical community who believe the province must follow the protocol established by Pfizer. Vinh says there is no flaw in this logic.

But the scientist also says that while there are pros and cons to both approaches, “people with expertise and experience with vaccines” tend to think of the three possible outcomes after delaying the second dose – less than that. immunity, neutral effect or enhanced effect – – the positive aspects will prevail.

“So I think we’ll have to calm down a bit. ”

A professor from the school of public health at the University of Montreal, Benoit Masse, is on the same wavelength, telling La Presse on Saturday that “the government made the right decision.


In the email Tania Muhanna received postponing her appointment for a second dose, health authorities assured her that “the effectiveness of the first dose, 14 days after administration, exceeds 90%”.

Is this figure correct? It was difficult to determine.

Dr Donald Vinh said the government’s assessment is not inaccurate but incomplete, lacking nuance on the potential range of protection that could be conferred after a stroke.

The immunity specialist says the reality is that “depending on how you do the math, it’s somewhere between 60 and 70 percent for the most part. It can go down to 52% in some people and 90% in others. ”

He explains why there are so many different numbers: “In the studies that were done for Pfizer and Moderna, the plan was for everyone to get two doses of the vaccine,” which is standard practice in clinical trials.

Sometimes extenuating circumstances prevent participants from receiving both doses, and this is what happened with the COVID vaccine – a few people only received one dose.

But as has happened with a small number of people, Vinh said, statistically the researchers end up with a wide range of efficacy results.

“This is what we call a confidence interval (CI)… how certain we are of an effect,” the doctor said.

So the question is, why doesn’t Pfizer tout the 90% efficacy of its vaccine?

Instead, the company told CTV News in a Jan.5 statement that the phase three trial showed immunity to start showing 12 days after the first dose, but only “52.4% the efficacy of the vaccine was observed between dose 1 and dose 2. ”

A Pfizer spokesperson added, “We can only support the use of the product according to the label and indication agreed with Health Canada.

Vinh suggested the company was cautious.

“Pfizer is a business and as a business they don’t want to be sued, so they don’t want to over-sell the effect of a dose of their product,” he said.

But he said the limited data from Pfizer he studied shows the protective effect ranges from 52% to around 90% – in his opinion, probably lying somewhere in the middle of that continuum, between 60 and 69%. .

That means, he says, if you have 100 people in the population and only 10 of them get two doses, you protect them up to 95%. But 90 p. 100 of the population of this population is still at risk of contracting the disease.

“If you give all the first doses to 100 people, which reduces their risk by 60%, you dramatically reduce your hospitalization rates. And again – all with the aim of preventing hospitalizations and deaths, ”he said.

It’s like wearing a seat belt, he suggested. “Seat belts reduce the risk of serious injury by 50%.”


A major problem is how to determine the optimal duration between dose 1 and dose 2.

The three to four week gap came about because US drug companies were working under the administration’s Operation Warp Speed, to speed up discovery amid a pandemic and establish whether the vaccines were safe. and efficient.

“Most of the other studies wouldn’t have done it as quickly, they wouldn’t have given the doses that come close, and there are biological reasons why it might even be suboptimal,” said the Dr Vinh.

The question is “will a delay between the first and the second dose compromise the effectiveness of the vaccine,” he said, “and the answer is we don’t know. ”

Dr. Vinh will investigate this issue for the federal government as the vaccine rolls out.

However, the majority of all other vaccines in Canada given in two doses require at least a month and even two months between the first and second.

“And when we say at least two months – there’s nothing magical that happens at a month or two months. What we’re saying is it’s at least that point in time, ”Vinh said, reiterating that there is a likely chance that a delay of one to two more months between doses doesn. ‘has no impact on safety and efficacy and may even lead to improvements.

He says that is why, when the limited data they have from Pfizer on the subject are combined with their extensive knowledge of how vaccines work and the immune system, a good argument can be made for delaying the second dose.


The short answer is no, but the strategy employed in several jurisdictions has been revised.

Health Canada is the regulatory body that analyzed the data submitted by Pfizer and Moderna and then approved the vaccines – because it approves all drugs used across the country.

It can only approve the indications that have been studied and submitted by the companies.

In a statement to CTV News, a spokesperson for Health Canada and the Public Health Agency of Canada said, “The federal government is not currently required to withhold the second dose of the vaccine series.

As with any possible extended delay between doses, Health Canada “recommends” that Canadians receive both doses of the same vaccine, “as close as possible to the authorized dosing schedule for each vaccine.”

However, the scientific and ethical implications of “widely distributing all doses of vaccine immediately to immunize more people”, according to Health Canada, compared to keeping doses in reserve for the second vaccine, have been assessed by the National Advisory Committee of the United Nations. ‘immunization.

The regulatory agency has announced that it will update its analysis soon.


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