MONTREAL -- As soon as the Quebec government announced it would take the Pfizer COVID vaccines reserved for second doses, and distribute them so they would be able to immunize more people in high-risk groups, Dr. Donald Vinh of McGill University said misinformation started to spread.

“I actually heard people in my institution say the second dose was cancelled, and I said that’s not correct. There is no plan by any government -- by the provincial or federal governments -- to cancel the second dose," said Vinh.

Appointments for booster shots will, however, be delayed beyond the three-week interval recommended by the manufacturer, as a result of the government’s decision.

It’s a policy shift that has many questioning the efficacy of a single dose, and whether the province is even permitted to go off in a different direction with the vaccination schedule. There is no shortage of opinions.

The microbiologist and infectious diseases specialist hopes to help clear up some of the confusion and adds that the government needs to “communicate clearly with the lay public...and address the concerns that people have, especially the hesitant ones.”

That includes people like Tania Muhanna, who described herself as “vaccine-hesitant” when we met her just before Christmas, as she was mulling over whether or not to get the COVID vaccine.

Now, the patient-attendant at a long-term care centre in Dorval says she feels like she’s had the rug pulled out from under her.

Though she’s never been anti-vaccine and gets an annual flu shot, Muhanna did have concerns about the COVID vaccine. She said many of her co-workers did too.

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

She decided to take the plunge. Muhanna got her first dose of the Phizer COVID vaccine on Dec. 27 and said she suffered no ill effects other than “a bit of arm tenderness” at the site of injection.

“There’s so much focus on the possible negative side effects. I went and I was completely, utterly fine,” Muhanna said in an interview with CTV News. 

Ultimately, the Montreal front-line worker says she asked herself if she was “willing to take that risk of not vaccinating and possibly get something that can possibly kill you, or take something that may or may not have side effects."

Muhanna concluded that getting the vaccine was the “most appropriate decision for myself,” because of her job, her desire to keep her family safe and because the number of cases was “skyrocketing again.”

But on Jan. 8, Muhanna received an email from West Island health authorities that stated her “appointment for the second dose of the Pfizer vaccine has been cancelled.”

The note she sent to CTV News went on to say she’d be contacted for a new appointment when a second dose is available, but that because of a new Health Ministry directive “it is no longer mandatory that it be done within 21 days after the first dose to ensure maximum protection.”

“This is outrageous and unacceptable,” Muhanna said, since she’d signed a consent form that explained the second dose protocol.


The move to stop setting aside second doses is due to the short supply of the American-produced vaccine.

The federal government says vaccine delivery will ramp up next month.

Deciding to use the stockpiled second doses immediately follows “the principle of utilitarianism, meant to benefit the greatest number of people,” Vinh said, as the virus rages and hospitals and health-care workers reaching their breaking points.

The province of Ontario and some other countries are taking the same path as Quebec. On Friday night, incoming U.S. President Joe Biden announced his administration will also release nearly all available vaccine doses for the same reason.

But just because it’s a practical plan that addresses the urgency of the situation doesn’t mean there’s no basis for it in science, said Vihn, who also sits on a COVID task force for the federal government.

Both levels of government rely on the work of advisory committees composed of scientists, clinicians, legal experts and ethicists when making policy decisions like this one.

The Comite sur l’immunisation du Quebec would have reviewed the literature, the existing supply issue and the COVID rates before recommending the approach, he said.

“What we’re doing (in Quebec) is a little off-script -- that’s true," Vinh said.

But there is “biological plausibility why 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- won’t make any difference, at six to eight weeks."

He’s heard the serious concerns expressed by some in Montreal’s medical community, who think the province needs to follow the protocol laid out by Pfizer. Vinh says there’s no flaw in that logic.

But the scientist also says while there are pros and cons to both approaches, “people with expertise and experience with vaccines,” tend to think that of the three possible outcomes after delaying the second dose -- less immunity, neutral effect or improved effect -- the positives will win out.

“So I think we will have to calm down a little bit.”

A professor at Universite de Montreal’s school of public health, Benoit Masse, is on the same page, 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 “the effectiveness of the first dose, 14 days after administration exceeds 90 per cent.”

Is that figure accurate? It's been difficult to determine.

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

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

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

Sometimes, extenuating circumstances prevent the participants from receiving both doses, and that’s what happened with the COVID vaccine - a few people got only one dose.

But because that occurred with a small number of people, Vinh said, statistically, researchers end up with a large range of efficacy results.

“It’s what we call a confidence interval (CI) certain we are of an effect,” the doctor said.

The question, then, is why doesn’t Pfizer tout the 90 per cent efficacy of its vaccine?

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

A Pfizer spokesperson went on to say, “we can only support usage of the product according to the label and indication agreed upon with Health Canada.”

Vinh suggested the company is being prudent.

“Pfizer is a business and as a business, they don’t want to get sued so they don’t want to oversell the one-dose effect of their product," he said.

But he said the limited Pfizer data he’s studied shows the protective effect ranges from 52 per cent to about 90 per cent -- in his opinion, likely settling somewhere in the middle of that continuum, at 60 to 69 per cent.

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 per cent. But you still have 90 per cent of the people in that population at risk for disease.

“If you give all of the first doses to 100 people, lowering their risk by 60 per cent, you dramatically decrease your hospitalization rates. And again -- all of this is with the intention of preventing hospitalizations and deaths,” he said.

It’s like wearing a seatbelt, he suggested. “Seat belts reduce the risk of severe injury by 50 per cent.”


A major issue is how to determine the optimal length of time between dose 1 and dose 2.

The three-to-four-week interval came about because the drug companies in the U.S. were working in the context of the administration's Operation Warp Speed, to accelerate discovery amid a pandemic and establish if the vaccines were safe and effective.

“Most other studies would not have done it that rapidly, they would not have given the doses that close together, and there are some biological reasons why that would maybe even be sub-optimal,” said Dr. Vinh.

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

Dr.Vinh will be studying that very question for the federal government as the vaccine is rolled out.

The majority of all other vaccines in Canada, however, that are administered in two doses require at least a month and even two months in between the first and second.

“And when we say at least two months -- there’s nothing magical that happens at one month or two months. What we say is that it's at least that time point away,” Vinh said, reiterating there is a probable chance that a delay of one to two months more between doses will have no impact on safety and efficacy and could even lead to improvements.

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


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

Health Canada is the regulatory body that analyzed the data Pfizer and Moderna submitted and subsequently approved the vaccines -- as it approves all medications used across the country.

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

In a statement to CTV News, a spokesperson for both Health Canada and the Public Health Agency of Canada said “there is currently no requirement from the federal government to hold back the second dose in the vaccine series.”

As for 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 regimen for each vaccine.”

However, the scientific and ethical implications of “widely distributing all vaccine doses right away to immunize more people,” Health Canada says, compared to keeping doses on reserve for the second shot, has been evaluated by the National Advisory Committee on Immunization.

The regulatory agency says it will update its analysis soon.