Jeanne Hennebury, 93, receives the Pfizer-BioNTech COVID-19 mRNA vaccine from Vena Anderson at a pharmacy prototype clinic in Halifax on Tuesday, March 9, 2021. CANADIAN PRESS/Andrew Vaughan

Jeanne Hennebury, 93, receives the Pfizer-BioNTech COVID-19 mRNA vaccine from Vena Anderson at a pharmacy prototype clinic in Halifax on Tuesday, March 9, 2021. CANADIAN PRESS/Andrew Vaughan

Research raises questions over delayed second vaccine doses for seniors

A Vancouver study found long-term care residents had a weaker immune response to their first dose of the Pfizer-BioNTech vaccine than younger healthy adults

More questions are being raised about how long second shots of the COVID-19 vaccine can be delayed for seniors and other immunocompromised people.

The federal body that advises how vaccines are deployed said Thursday it’s reviewing a Vancouver study that found long-term care residents had a weaker immune response to their first dose of the Pfizer-BioNTech vaccine than younger healthy adults.

After supplies slowed to a trickle earlier this year, the National Advisory Committee on Immunization said provinces and territories can delay second doses by as long as four months.

That’s instead of the recommended schedule that spaces out the two-dose Pfizer-BioNTech and Moderna vaccines by three to four weeks, and the AstraZeneca product by four to 12 weeks.

Committee chair Dr. Caroline Quach said Thursday that NACI is looking at the Vancouver research, which found a weaker antibody response among older recipients but did not measure whether seniors were more likely to fall sick or die.

She said the findings will be assessed along with data from Quebec and the United Kingdom.

“What is so difficult with this disease is that there is no correlate of protection. That means that the presence and quantity of antibody present does not mean protection, or lack thereof,” Quach said in an email to The Canadian Press.

“Based on all those data, NACI will see if exceptions to the extended interval are necessary, keeping in mind that we are managing risk at a population level: the more people are vaccinated, the more likely we are to stop transmission, which will also be protective for the most vulnerable who may not mount an optimal response.”

The Vancouver data, funded by the COVID-19 Immunity Task Force, has yet to be peer-reviewed but adds to concerns about the rollout strategy of provinces including Ontario, Manitoba, Saskatchewan, Alberta, and British Columbia.

Task force director Dr. Tim Evans said the findings underscore a need to monitor senior recipients very carefully after their first shot.

“The immune response is so complicated and we still don’t fully understand what are called the correlates of protection,” Evans said from Montreal, where he is director and associate dean of the school of population and global health at McGill University.

“The most important takeaway from this study is we have to be very vigilant in monitoring the followup for the elderly, or immunocompromised with respect to extending the vaccine dose beyond what’s recommended.”

Evans stressed that older people in both long-term care and the community are well-protected for many weeks by a single dose of an mRNA vaccine, but said there may be limits to how long some people should wait for their second dose.

He said COVID-19 vaccines have already been associated with dropping hospitalizations and deaths in Canada, but expected NACI may have to refine its advice for how they be used in various populations.

“We’ve got multiple vaccines, they all work a little bit differently and so we know that we don’t have a one-size-fits-all approach,” he said, adding that long-term care residents may be more vulnerable than seniors in the community.

“We’re going to have to get used to working with different approaches for different age groups with different vaccines over the coming months as the vaccine rollout continues.”

The director of geriatrics at Toronto’s Sinai Health said a delayed-dose strategy makes little sense for a population already known to have a less-robust response to vaccines.

Dr. Samir Sinha said there’s already enough evidence for NACI to revise its advice, suggesting some urgency as he pointed to statistics that find 96 per cent of COVID-19 linked deaths are people over the age of 60.

“As a geriatrician, I’m becoming increasingly uncomfortable about the strategy of delaying these doses for older people and in particular, older people living in congregate care settings, and those who are highly vulnerable,” said Sinha.

Sinha acknowledged that NACI considers an array of factors in determining its guidelines and at the time of its March 3 decision, pressures included dwindling vaccine supplies, emerging variants and fears of a looming third wave.

Earlier Thursday, Health Canada’s chief medical adviser Dr. Supriya Sharma noted her agency – a separate body from NACI – approved the vaccines for use according to their respective labels.

She also said NACI’s advice will evolve as new science becomes available.

“I think it does make sense that we potentially have a more nuanced recommendation around that delayed second dose, but those conversations are ongoing,” Sharma said.

Principal investigator Dr. Marc Romney, an associate professor at the University of British Columbia, said not only did his study find LTC residents produced lower levels of antibodies, the antibodies they produced were less adept at blocking the SARS-CoV-2 virus from binding to its target cells.

“You don’t want to be leaving a large segment of society that’s already borne the brunt of the pandemic vulnerable to infection, awaiting a second dose – that is the potential issue here,” said Romney, medical leader for medical microbiology and virology at St. Paul’s Hospital, Providence Health Care.

“Hospitalizations are increasing again. And we have seen some outbreaks in long-term care facilities where people have been vaccinated, which is also concerning.”

He and a research team co-led by Dr. Zabrina Brumme of the BC Centre for Excellence in HIV/AIDS and Dr. Mark Brockman of Simon Fraser University analyzed blood samples collected from 18 long-term care residents and 12 healthcare workers.

They were taken in late 2020 and early 2021 before vaccination and compared to changes after participants received their first dose.

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

Just Posted

The Regional District of Nanaimo plans to make its operations more efficient as it works on long-term goals around carbon-neutrality. (PQB News file photo)
Regional District of Nanaimo works to become carbon neutral by 2032

RDN committee of the whole members endorse plan developed by consultant

The Millstone River in Nanaimo. (News Bulletin file photo)
Regional district looks at value of Nanaimo’s natural assets

Report focused on the Millstone River could inform future decisions on corporate asset management

Protesters gather along the Pearson Bridge on Terminal Avenue in downtown Nanaimo last month as part of an event called Worth More Standing. (News Bulletin file photo)
LETTER TO THE EDITOR: B.C. hasn’t managed forests properly

Protesters opposing logging in Fairy Creek speak for many British Columbians, say letter writers

Nanaimo singer Victoria Vaughn recently released an EP with local producer Austin Penner. (Photo courtesy Taylor Murray)
Nanaimo singer and recent VIU grad releases EP about becoming an adult

Victoria Vaughn’s ‘Growing Pains’ recorded with local producer Austin Penner

The B.C. Centre for Disease Control has listed Harbour Air and Air Canada flights to and from Nanaimo, from April 3, 4 and 12, on its list of flights with COVID-19. (News Bulletin file)
COVID-19 cases reported for Air Canada, Harbour Air flights, says disease control centre

Nanaimo flights for April 3, 4 and 12 listed on BCCDC’s list of flights with COVID-19

Pat Kauwell, a semi-retired construction manager, lives in his fifth-wheel trailer on Maxey Road because that’s what he can afford on his pension, but a Regional District of Nanaimo bylaw prohibits using RVs as permanent dwellings, leaving Kauwell and others like him with few affordable housing options. (Chris Bush/News Bulletin)
Housing crunch or not, it’s illegal to live in an RV in Nanaimo

Regional District of Nanaimo bylaw forcing pensioner to move RV he calls home off private farm land

People are shown at a COVID-19 vaccination site in Montreal, Sunday, April 18, 2021, as the COVID-19 pandemic continues in Canada and around the world. THE CANADIAN PRESS/Graham Hughes
Nothing stopping provinces from offering AstraZeneca vaccine to all adults: Hajdu

Health Canada has licensed the AstraZeneca shot for use in people over the age of 18

Deputy Prime Minister and Minister of Finance Chrystia Freeland responds to a question during Question Period in the House of Commons Tuesday December 8, 2020 in Ottawa. The stage is set for arguably the most important federal budget in recent memory, as the Liberal government prepares to unveil its plan for Canada’s post-pandemic recovery even as a third wave of COVID-19 rages across the country. THE CANADIAN PRESS/Adrian Wyld
Election reticence expected to temper political battle over federal budget

Opposition parties have laid out their own demands in the weeks leading up to the budget

Noel Brown, Snuneymuxw First Nation carver, observes the house post he carved, which now is situated in front of the Kw’umut Lelum centre on Centre Street in Nanaimo. (Karl Yu/News Bulletin)
House post representative of work of Kw’umut Lelum in Nanaimo

Snuneymuxw First Nation artist Noel Brown’s carved red cedar house post unveiled Friday, April 16

(Black Press file photo).
UPDATED: Multiple stabbings at Vancouver Island bush party

Three youths hospitalized after an assault in Comox

A syringe is loaded with COVID-19 vaccine at a vaccination clinic run by Vancouver Coastal Health, in Richmond, B.C., Saturday, April 10, 2021. THE CANADIAN PRESS/Jonathan Hayward
B.C. to open up COVID vaccine registration to all B.C. residents 18+ in April

Registration does not equate to being able to book an appointment

Russ Ball (left) and some of the team show off the specimen after they were able to remove it Friday. Photo supplied
Courtenay fossil hunter finds ancient turtle on local river

The specimen will now make its home at the Royal BC Museum

Selina Robinson is shown in Coquitlam, B.C., on Friday November 17, 2017. British Columbia’s finance minister says her professional training as a family therapist helped her develop the New Democrat government’s first budget during the COVID-19 pandemic, which she will table Tuesday. THE CANADIAN PRESS/Darryl Dyck
B.C. finance minister to table historic pandemic-challenged deficit budget

Budget aims to take care of people during pandemic while preparing for post-COVID-19 recovery, Robinson said

Most Read