Deputy chief public health officer Dr. Howard Njoo responds to a question during a news conference, Tuesday, Jan. 12, 2021 in Ottawa. THE CANADIAN PRESS/Adrian Wyld

Deputy chief public health officer Dr. Howard Njoo responds to a question during a news conference, Tuesday, Jan. 12, 2021 in Ottawa. THE CANADIAN PRESS/Adrian Wyld

UPDATE: Data suggests Pfizer vaccine may be almost as good after 1 dose as 2

Pfizer to ship nearly three million doses over next six weeks, Moderna more than 1.4 million.

There is compelling evidence that a single dose of COVID-19 vaccines may provide almost as much protection as giving two doses, Canada’s deputy chief public health officer said Thursday.

Dr. Howard Njoo said the advisory committee of federal and provincial public health officers is having an active discussion about whether Canada would be better served to delay the second doses of vaccines in a bid to give protection to more vulnerable people quicker.

“These are what I would call early data in terms of a vaccine effectiveness or studies,” he said. “And the indications are that there’s a good level of protection after just one dose.”

Canada intends to vaccinate three million people with two doses by the end of March.

More than 990,000 Canadians have received at least one dose, and about one-third of those have also received their second doses.

RELATED: Senior homes stay safe as B.C. finds 427 more cases of COVID-19

RELATED: Two young adults from Cowichan Tribes have died of COVID-19

Quebec’s immunization committee went as far Thursday as to recommend nobody get a second dose until a first dose is injected into everyone in six high-risk groups, including people over 70, health-care workers, and people who live in long-term care homes and retirement residences.

The committee reported that single doses have been 80 per cent effective at preventing COVID-19 so far among long-term care residents and health workers who were vaccinated.

Questions about delaying the second doses arose almost as soon as vaccinations began in December, prompting a whirlwind of debate among scientists about the ethics of “going off label.”

Pfizer-BioNTech and Moderna’s vaccines — the two currently authorized in Canada — were tested by giving two doses, 21 days and 28 days apart respectively.

But Dr. Danuta Skowronski, the epidemiology lead for influenza and emerging respiratory pathogens at the British Columbia Centre for Disease Control, said data show two weeks after one dose of either vaccine, the protection against COVID-19 was almost as good as what was found after two doses.

Skowronski and Dr. Dr. Gaston De Serres from the Institut national de santé publique du Québec made the case in a letter published in the New England Journal of Medicine this week.

Moderna reported itself that two weeks after one dose, those who got the vaccine were 92 per cent less likely to develop COVID-19 symptoms.

Pfizer and BioNTech, whose vaccine uses similar genetic technology to Moderna’s, said their vaccine was 52 per cent effective after one dose, but 94.5 per cent effective after two.

Skowronski said Pfizer started measuring illness as soon as the injections were given, which she said is “unreasonable.”

“It’s basic vaccinology that you don’t expect the vaccine to activate the immune system instantaneously,” she said, in an interview with The Canadian Press.

Skowronski said if you wait two weeks to start counting infections, there were 92 per cent fewer infections of COVID-19 among those who got one dose of the vaccine, compared with those who got the placebo.

At that level of protection, she said “we need to get a first dose into our priority populations, and the most vulnerable of those at greatest risk of severe outcomes and the precious resource of our front-line health-care workers.”

She said the second dose should eventually be given but said there isn’t a maximum time she would put on how long to wait.

Pfizer has issued caution about adjusting the dosing schedule but said the decision to do so rests with local authorities.

“We at Pfizer believe that it is critical for health authorities to carry on surveillance on implemented alternative dosing schedules to ensure that vaccines provide the maximum possible protection,” the company’s statement reads.

Canada’s National Advisory Committee on Immunization said in January that the recommended schedule should be followed wherever possible but that delaying a second dose up to six weeks could be beneficial, particularly with a shortage of supplies and a fast-spreading virus.

Skowronski said waiting six weeks instead of three or four for a second dose won’t do much.

“That’s not maximizing coverage that we need to undertake with the scarcity of the vaccine that is available now.”

Several provinces have been delaying the second doses a couple of weeks, particularly as deliveries of both Pfizer-BioNTech’s vaccine and Moderna’s slowed to a crawl in mid-January.

Those delays appear to be over. Pfizer says it will ship nearly three million doses over the next six weeks, and Moderna promises to ship more than 1.4 million.

With the two authorized vaccines, and the two-dose schedule followed, Canada expects to vaccinate 14.5 million people by the end of June and all Canadians who want to be immunized by the end of September.

A new vaccination schedule issued Thursday shows if the other three vaccines currently being reviewed get approved by Health Canada, 24.5 million Canadians could be vaccinated before Canada Day.

Mia Rabson, The Canadian Press

Like us on Facebook and follow us on Twitter.

Want to support local journalism? Make a donation here.

Coronavirus

Just Posted

Recreation therapy staff Karen Baker and Jenessa Dunkle dressed up for the tea on the Titanic, held on the 109th anniversary of the sinking of the vessel.
photo submitted
109 years after the sinking, the Titanic disaster is still remembered in Castor

Residents of Castor’s long term care facility were treated to an immersive celebration of the vessel

Alberta’a chief medical officer of health Dr. Deena Hinshaw said Thursday that there are more than 328,000 vaccine appointments booked over the next seven days. (Photo by Chris Schwarz/Government of Alberta)
Alberta surpasses 2 million doses administered of COVID-19 vaccine

Red Deer down to 835 active cases of COVID-19

Alberta Premier Jason Kenney arrives at the 2021 budget in Edmonton, Thursday, Feb. 25, 2021.
‘We did not unite around blind loyalty to one man’:Kenney faces internal call to quit

Senior backbench member Todd Loewen, in a letter posted on Facebook, called on Kenney to resign

Alberta continues to wrestle with high COVID-19 case numbers. (NIAID-RML via AP)
Red Deer up to 858 active cases of COVID-19

Province reports additional 1,799 cases of the virus

Marc Kielburger, screen left, and Craig Kielburger, screen right, appear as witnesses via video conference during a House of Commons finance committee in the Wellington Building in Ottawa on Tuesday, July 28, 2020. The committee is looking into Government Spending, WE Charity and the Canada Student Service Grant. THE CANADIAN PRESS/Sean Kilpatrick
Trudeau didn’t violate conflict rules over WE Charity, watchdog says

Federal ethics commissioner Mario Dion found that former finance minister Bill Morneau did violate the rules

Chris Scott, owner of The Whistle Stop Cafe, was put in handcuffs after an anti-restriction protest Saturday in the parking lot of the business. (Screenshot via The Whistle Stop Facebook page)
Alberta RCMP investigating possible threat to police after Mirror rally

Online images show RCMP members, vehicles in crosshairs of a rifle

An Israeli attack helicopter launches flares as he flies over the Israeli Gaza border, southern Israel, Thursday, May 13, 2021. (AP Photo/Ariel Schalit)
Singh calls for halt on Canadian arms sales to Israel as violence escalates in region

Government data shows Canada sent $13.7 million in military goods and technology to Israel in 2019

New homes are built in a housing construction development in the west-end of Ottawa on Thursday, May 6, 2021. THE CANADIAN PRESS/Sean Kilpatrick
Budget’s foreign-homebuyers tax could bring in $509 million over 4 years, PBO says

Liberals are proposing a one per cent tax on vacant homes owned by foreign non-residents

A Canadian flag patch is shown on a soldier’s shoulder in Trenton, Ont., on Thursday, Oct. 16, 2014. The Canadian Forces says it has charged one of its members in the death of an army reservist from British Columbia during a training exercise at a military base in Alberta last year. THE CANADIAN PRESS/Lars Hagberg
Canadian Forces member charged in death of army reservist during training exercise

Cpl. Lars Callsen has been charged with one count of negligence

A youth plays basketball in an otherwise quiet court in Toronto on Saturday April 17, 2021. The Canadian Civil Liberties Association is urging the federal and provincial governments to fight COVID-19 pandemic by focusing on proven public health policy interventions including paid sick leave, and education rather than punitive enforcement measures. THE CANADIAN PRESS/Chris Young
Provinces issued more COVID-19 tickets during 2nd wave: CCLA report

‘A pandemic is a public health, not a public order, crisis,’ reads the report

Prime Minister Justin Trudeau holds a press conference in Ottawa on Tuesday, May 11, 2021. Trudeau is rejecting accusations from Alberta’s justice minister that his federal government is part of a trio rooting for that province’s health system to collapse due to COVID-19. THE CANADIAN PRESS/Sean Kilpatrick
Alberta justice minister sorry for saying feds, others rooting for COVID disaster

Earlier Tuesday, prior to Madu’s apology, Trudeau rejected the accusations

In this Monday, March 15, 2021 file photo a vial of AstraZeneca vaccine is pictured in a pharmacy in Boulogne Billancourt, outside Paris. Questions remained Wednesday about the future of the Oxford-AstraZeneca vaccine in Canada, as Manitoba limited use of the shot and Ontario announced it planned to save an incoming shipment to use as second doses. THE CANADIAN PRESS/AP/Christophe Ena, File
Questions remain about the future of the Oxford-AstraZeneca shot in Canada

More than two million Canadians have received AstraZeneca and 17 have been confirmed to have VITT

Most Read