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

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

The current boat used by Rugged Coast Research Society for remote shoreline cleanup operations will be replaced by a landing craft that will allow society members to haul four times as much marine garbage per trip from Vancouver Island’s remote shorelines. (Agathe Bernard photo/Rugged Coast Research Society)
Nanaimo-based research group needs bigger boat for coastal cleanups

Rugged Coast Research Society raising cash for landing craft to pull trash from remote shorelines

Pet owners are leaving more dog waste than ever before on Nanaimo’s paths and trails, says letter writer. (Stock photo)
LETTER TO THE EDITOR: Dog owners need to pick up after their pets

Letter writer says he’s ‘disgusted’ by dog walkers not picking up their dog waste

The Nanaimo African Heritage Society is capping its month of Black History Month celebrations with a virtual gala on Sunday, Feb. 28. (News Bulletin photo)
Nanaimo African Heritage Society presents virtual Black History Month gala

Event to feature a variety of speakers and performers

(Black Press file)
Nanaimo Ladysmith Public Schools reports COVID-19 exposure at Cedar Elementary

School district says Island Health has completed contact tracing

Staff from the Marine Mammal Rescue Centre, passersby, RCMP and Nanaimo Fire Rescue carried a sick 300-kilogram steller sea lion up the steep bluff at Invermere Beach in north Nanaimo in an attempt to save the animal’s life Thursday. (Photo courtesy Marine Mammal Rescue Centre)
300-kilogram sea lion muscled up from the beach in rescue attempt in Nanaimo

Animal dies in spite of efforts of marine mammal rescue team, emergency personnel and bystanders

1957 photo shows Six Mile House-sponsored #4 1932 Ford stock car with Frank Morris (from left), Ted Mackenzie, Bill Sim and driver Gerry Sylvester. (Bud Glover/Victoria Auto Racing Hall of Fame)
Memories race as Western Speedway approaches its finish line

‘It was life to us:’ Vancouver Island racers, crew will never forget what the track gave them

BC Ferries experienced heavy traffic on Feb. 27 following cancellations the day before due to strong winds and adverse weather. (Black Press Media file photo)
BC Ferries sailings fill up quickly after Friday cancellations due to high winds

Waits expected on Swartz Bay-Tsawwassen route, Horseshoe Bay-Departure Bay route

Wayne Allen's graduation photo from Chemainus Secondary School. (Photo submitted)
Brother charged with murder in Vancouver Island teenager’s Ontario death

Jesse James Allen stands accused in the death of Wayne Allen, a 2020 Chemainus Secondary grad

Nanaimo Ladysmith Public Schools is preparing a rapid response team proposal for submission to the B.C. Ministry of Education. (Chris Bush/News Bulletin)
Nanaimo-Ladysmith school district chosen to field COVID-19 rapid response team

Team to consist of SD68 and Island Health staff, according to B.C. Ministry of Education

A 50-year-old man was stabbed in an altercation that started with a disagreement about physical distancing. (File photo)
Argument about physical distancing leads to stabbing in Nanaimo

Suspect arrested on Gabriola Island an hour after incident Wednesday, Feb. 24

Snuneymuxw artist Eliot White-Hill, Kwulasultun is among the artists participating in the Nanaimo Art Gallery’s Rain Shadow exhibit. His piece, ‘We Fell from the Sky/Together and Apart,’ depicts a Snuneymuxw creation story. (Josef Jacobson/News Bulletin)
Nanaimo Art Gallery exhibit explores the ways people think about place

‘Rain Shadow’ features work mostly by Vancouver Island and Gulf Island artists

A Vancouver restaurant owner was found guilty of violating B.C.’s Human Rights Code by discriminating against customers on the basis of their race. (Pixabay)
Vancouver restaurant owner ordered to pay $4,000 to customers after racist remark

Referring to patrons as ‘you Arabs’ constitutes discrimination under B.C.’s Human Rights Code, ruling deems

Dasher is back home with mom Christine Girvin thanks to some help from BC Ferries staff. Photo supplied
The cat came back, with help from BC Ferries staff

After Dasher made a dash, staff in Comox found her and got her home safe

Most Read