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

Saanich Fire Department. (Black Press Media file photo)
Fire displaces three Saanich families from two homes

Saanich firefighters found the fire had spread to a neighbouring home upon arriving

Oaklands Elementary’s Division 5 Grade 4/5 class posed with Leila Bui (middle), her dad Tuan Bui (crouching to her left) and mom Kairry Nguyen (right) after presenting the family with a cheque for $710 raised by the students during a necklace sale in December 2020. (Photos courtesy Kairry Nguyen)
Victoria students raise funds for girl seriously injured when struck by vehicle in crosswalk

Oaklands Elementary class contributes to purchase of all-terrain wheelchair for Leila Bui

An Island Health nurse prepares a dose of COVID-19 vaccine. (Photo courtesy Island Health)
Health authority opening 19 clinics to immunize Vancouver Island residents

Health authority anticipates more than 40,000 people will be immunized over the next month

Alphabet Zoo Early Learning Centre wants to relocate from Langford to 3322 Fulton Rd. in Colwood, but has not been approved for a P-6 zoning by Colwood council. Residents who neighbour the property, have expressed concern to the Goldstream Gazette regarding the potential daycare site. Neighbours Ryan Landa and Selene Winchester said the noise of construction has been disruptive to the area, and the property is not suitable for a daycare. (Photo contributed/Ryan Landa)
Proposed West Shore daycare stirs up controversy amongst neighbours

Neighbouring property owners are concerned about traffic, noise that a daycare would bring to the area

According to Statistics Canada, new housing starts and value of building permits in Greater Victoria rose in January 2021 compared to January 2020. (Black Press Media File)
New housing starts, value of building permits up in Greater Victoria

Cost of new housing also rising in region, now in excess of $1.15 million for a new detached home

The Pfizer-BioNTech COVID-19 vaccine is administered to a personal support worker at the Ottawa Hospital on Tuesday, Dec. 15, 2020 in Ottawa. Doctors in Alberta have signed an open letter asking for prioritized vaccination of health-care staff who work directly with patients on dedicated COVID-19 units. THE CANADIAN PRESS/Adrian Wyld
COVID vaccines for seniors in B.C.: Here’s how to sign up

Seniors 90+, Indigenous seniors 65+ and Indigenous Elders can book starting March 8

Software engineer Shaimma Yehia, 40, has been forced to re-skill during the COVID-19 pandemic after more than six years of unsuccessfully applying for jobs in B.C.’s tech industry. (Submitted photo/Shaimma Yehia)
Why skilled immigrant women continue to be shut out of B.C.’s booming tech sector

Experienced software engineer Shaimma Yehia, 40, hasn’t found a job since she migrated to Canada 6 years ago

A woman walks through Toronto’s financial district on Monday, July 30, 2018. A new poll suggests most Canadians believe there’s still a long way to go to achieve gender equality in this country. THE CANADIAN PRESS/Graeme Roy
Canadians, especially women, say gender equality not achieved in Canada: Poll

Poll results themselves underscore the challenge, with more men believing equality had been achieved

This image provided by Harpo Productions shows Meghan, The Duchess of Sussex, left, in conversation with Oprah Winfrey. (Joe Pugliese/Harpo Productions via AP)
Race, title and anguish: Meghan and Harry explain royal rift

Meghan said she struggled with concerns within the royal family about her son’s skin colour

Const. Allan Young. Photo: Abbotsford Police Department
Manslaughter charge laid in Nelson death of Abbotsford police officer

Allan Young died after an incident in downtown Nelson last summer

(The Canadian Press)
‘Worse than Sept. 11, SARS and financial crisis combined’: Tourism industry in crisis

Travel services saw the biggest drop in active businesses with 31 per cent fewer firms operating

The Port Alice pulp mill has been dormant since 2015. (North Island Gazette file photo)
Parts recycled, life returning to inlet as as old Port Alice mill decommissioned

Bankruptcy company oversees de-risking the site, water treatment and environmental monitoring

The Conservation Officers Service is warning aquarium users after invasive and potentially destructive mussels were found in moss balls from a pet store. (BC Conservation Officers Service/Facebook)
Aquarium users in B.C. warned after invasive mussels found at pet store

Conservation officers were told the mussels were found in a moss ball from a Terrace pet store.

Most Read