QUEBEC CITY -- Quebec public health officials said Thursday that provincial advisors have recommended a prolonged COVID-19 vaccination schedule of up to 90 days between the first and second dose -- more than double what a national advisory committee recommended a day earlier.

“In our context, that is the best strategy,” said Health Minister Christian Dubé at a Thursday press conference on Quebec’s vaccination progress.

Quebec announced in late December it would be delaying second doses or "booster shots" of the vaccine, but the province hadn't said until Thursday what kind of delay it had in mind.

Provincial officials now say the second dose should come between 42 and 90 days after the first.

Such a schedule would allow the province to give the vaccine to more people who would otherwise have to wait for their first dose, said the health officials.

A delay of 90 days is much longer than what’s been recommended by Pfizer (21 days, for its vaccine), Moderna (28 days, for its vaccine), and federal public health advisors in their recommendation on Wednesday (up to 42 days for both vaccines).

However, that national advisory panel, called NACI, said Thursday that provinces have some leeway to make their own decisions and they aren't opposing Quebec's 90-day timeline.

Canada's Deputy Chief Public Health Officer, Dr. Howard Njoo, said that certain provinces' "exceptional circumstances" may mean they need to depart from federal recommendations.

"It is sort of the interplay between the actual epidemiology, on the ground, the fact that there is a obviously increased rate of cases, hospitalizations," said Njoo, and the vaccine guidelines.


So why is the province talking about 90 days?

Health Ministry advisor Dr. Richard Massé said Quebec experts believe it's likely that immunity will last longer than 42 days, as recommended by the NACI panel, but clinical trials have not extended past that.

What they're relying on instead is past experience with other vaccines.

“What we have is the experience working with many vaccines,” said Massé. “Immunity is not something that is ‘on’ or ‘off.'”

While Quebec's Ministry of Health has said that a single dose can provide up to about 90 per cent efficacy against the virus, Pfizer says that one dose alone is just 52.4 per cent effective.

Massé told reporters the discrepancy comes from different and more specific analysis of Pfizer's trial data.

He said that Pfizer, when studying the issue, had been including people who had gotten their first dose but hadn't had time to build up immunity.

“It takes 12 to 14 days to have immunity," said Massé. "If you count people who get the disease two, three, five days after getting the vaccine, it's not really a failure of vaccination because immunity [hasn’t been built up]."

One expert told CTV News this week that there are big variations in the efficacy estimates because of the small sample size of people who got only the first shot in the Pfizer trial. That expert, Dr. Donald Vinh, said that in his opinion the efficacy is likely somewhere in the range of 60 to 69 per cent.

In a statement to CTV News, Pfizer Canada spokeperson Christina Antoniou reiterated earlier statements that Pfizer has not evaluated the efficacy of its vaccine on alternative dosing schedules.

"There are no data to demonstrate that protection after the first dose is sustained after 21 days," she said.

"We recognize that recommendations on alternative dosing intervals reside with health authorities and may include adapting public health recommendations in reaction to evolving circumstances during a pandemic," she wrote.

But for Pfizer, "as a biopharmaceutical company working in a highly regulated industry, our position is supported by the label and indication agreed upon with Health Canada and informed by data from our Phase 3 study."

Minister Dubé said the province has been talking to Pfizer. On Jan. 5, Pfizer told CTV News that Quebec had not informed the company before deciding to delay the second dose.

“We’ve had conversations with Pfizer,” said Dube, “to inform them as to why we were making those decisions.”

Earlier this week, Premier François Legault said that in discussions with the federal government, the province learned there may be a risk of losing Quebec's vaccine supply if Pfizer isn't happy with its dosing regime.

On Thursday, Pfizer's statement said the company "remain[s] committed to our ongoing dialogue with regulators, health authorities and governments, and to our continued data-sharing efforts to help inform any public health decisions aimed at defeating this devastating pandemic."

Both Massé and Dubé said they are hoping for an increased supply, since they would favour a shorter delay before the second dose if the province's deliveries of vaccine increase.

“Saving lives is a moral imperative,” said Dubé.

“The more doses we have, the more we’re going to be able to decrease the time between the first and second dose.”


With about 65 per cent of CHSLD residents already given a first dose, Dubé said Quebec will begin vaccinating residents of private seniors’ homes (RPAs) on Jan. 25.

He said that with a prolonged schedule between the first and second doses, the province can also consider vaccinating the general senior population sooner.

With new vaccine shipments arriving in the province this week, Dubé said 115,000 people have now been vaccinated.

In total, the province has received 162,000 doses so far. Dubé says Quebec is on track to increase that total to 250,000 in February.


Is delaying the second dose of the vaccine by 90 days going to work? Dr. Caroline Quach is an epidemiologist and in charge of the infection prevention and control unit at saint-Justine Hospital, on National Advisory Committee on Immunization. 

--With files from CTV's Kelly Greig