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

Village council saw an application to build a seven foot fence around a 3rd Ave. property in Nakusp. (Jocelyn Doll-Revelstoke Review)
Village of Nakusp sees application for seven foot fence

Council raised concerns about curb appeal

Elvira D’Angelo, 92, waits to receive her COVID-19 vaccination shot at a clinic in Montreal, Sunday, March 7, 2021, as the COVID-19 pandemic continues in Canada and around the world. THE CANADIAN PRESS/Graham Hughes
110 new cases of COVID-19 in Interior Health

Provincial health officers announced 1,005 new cases throughout B.C.

Tala MacDonald, a 17-year-old student at Mount Sentinel Secondary who is also a volunteer firefighter, has won the $100,000 Loran Scholarship. Photo: Submitted
West Kootenay student wins $100K scholarship

Tala MacDonald is one of 30 Canadians to receive the Loran Scholarship

Kristian Camero and Jessica Wood, seen here, co-own The Black Cauldron with Stephen Barton. The new Nelson restaurant opened earlier this month while indoor dining is restricted by the province. Photo: Tyler Harper
A restaurant opens in Nelson, and no one is allowed inside

The Black Cauldron opened while indoor dining is restricted in B.C.

First-year Selkirk College student Terra-Mae Box is one of many talented writers who will read their work at the Black Bear Review’s annual (virtual) launch on April 22. Photo: Submitted
In this image from NASA, NASA’s experimental Mars helicopter Ingenuity lands on the surface of Mars Monday, April 19, 2021. The little 4-pound helicopter rose from the dusty red surface into the thin Martian air Monday, achieving the first powered, controlled flight on another planet. (NASA via AP)
VIDEO: NASA’s Mars helicopter takes flight, 1st for another planet

The $85 million helicopter demo was considered high risk, yet high reward

New figures show Canadian housing prices outpacing those in other developed countries. (Black Press Media file photo)
Canadian housing prices fastest rising in the world

Relative to 2000, housing prices have risen by a factor of more than 2.5

Russ Ball (left) and some of the team show off the specimen after they were able to remove it Friday. Photo supplied
80-million-year-old turtle find on B.C. river exciting fossil hunters

Remains of two-foot creature of undetermined species will now make its home at the Royal BC Museum

Joudelie King wants to get out and live life to the fullest, but there are places she can’t go because they don’t meet her accessibility needs. (submitted photo)
New online tool provides accessibility map for people with disabilities

The myCommunity BC map provides accessibility info for nearly 1,000 locations in the province

British Columbia’s provincial flag flies in Ottawa, Friday July 3, 2020. THE CANADIAN PRESS/Adrian Wyld
Wildfire fanned by winds near Merritt prompts evacuation alert

BC Wildfire Service says the suspected human-caused blaze was fanned by winds

The Rogers logo is photographed in Toronto on Monday, September 30, 2019. THE CANADIAN PRESS/Tijana Martin
Rogers investigating after wireless customers complain of widespread outage

According to Down Detector, problems are being reported in most major Canadian cities

Flow Academy is located at 1511 Sutherland Avenue in Kelowna. (Michael Rodriguez - Capital News)
National fitness group condemns unlicensed Kelowna gym’s anti-vaccine policy

The Fitness Industry Council of Canada says Flow Academy is shining a negative light on the industry

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

Most Read