After a rough start, Canada is finally seeing an influx of COVID-19 vaccines. Experts say the surge in shots coming into Canada is a good opportunity to bump up appointments for second doses, particularly for the most vulnerable.
“The thinking was: Let’s get as many first doses into people’s arms as quickly as possible because some protection is better than no protection,” said Dr. Samir Sinha, the director of geriatrics at Sinai Health and the University Health Network, who led advocacy for seniors over the age of 70 to be prioritized for vaccinations in Ontario’s Phase 1.
“While that’s a really good strategy that works well in young people … We know that strategy doesn’t work as well in older people.”
Older populations don’t build enough of an immune response to a single dose, Sinha said, and with the vast majority of Canada’s COVID-19-related deaths still stemming from that age group, he sees value in readjusting plans.
Before vaccine shipments ramped up, Canada’s National Advisory Committee on Immunization (NACI) issued a recommendation to delay second doses for up to a maximum of four months — which deviates from manufacturers’ advice of three to four weeks.
Now, with Canada’s vaccine supply set to increase, some provinces are not only opening vaccine age eligibility to those as young as 12, but they’re also starting to shorten the interval between shots — meaning second doses are starting to go up for grabs. In Manitoba, that effort begins Friday for specific vulnerable groups.
Provincial differences
Many provinces have already started rolling out a strategy for second shots with a focus on high-risk groups.
Ontario — perhaps the loudest proponent of getting people fully vaccinated faster — took a step toward that effort this week, shortening the vaccine dose intervals specifically for health-care workers and people in certain high-risk groups.
Quebec took a similar step, bumping up second doses for Quebecers living with certain conditions or undergoing specific treatments, like for cancer, and those who have a poor immune response with only just one dose.
Alberta has a similar strategy, which came into play in April.
It’s a positive step, said Sinha, but it doesn’t necessarily consider age.
While nearly all elderly Canadians living in long-term care facilities have been fully vaccinated for some time now, he says there is a large population living in community settings that have not.
“People who are 80 and older, the ones who have the greatest risk of dying, we know they don’t mount as good an immune response to that first dose,” said Sinha.
“They are developing a response, but nothing as good as what a 40-year-old will develop.”
Only about 19 per cent of Canadians aged 80-plus and seven per cent of those aged 60-plus have been fully vaccinated, according to government data as of May 14.
The data also varies by province. The Northwest Territories, Nunavut and Yukon lead the pack in terms of fully vaccinating those 80 and older, with percentages in the high 80s and 90s.
In Ontario, only about 16 per cent of 80-plus have received two doses; in Quebec, it’s around seven per cent, about nine per cent in British Columbia, and about 25 per cent in Saskatchewan.
Saskatchewan has one of the more fulsome plans for second doses so far, which takes age into consideration.
The province’s vaccine delivery effort opened up second dose appointments on May 17, based on age or the date a person received their first shot. It expands the age and date ranges each week. So on May 24, a person aged 80-plus can book a second dose, as can those who received their first dose before March 1. It suggests Saskatchewan could close the four-month gap to three.
Sinha says it concerns him to see other provinces, like Ontario, leaving this population out right now, and believes there’s a case to be made about pivoting second doses to elderly adults rather than use supply to give healthy teens first doses.
But it doesn’t have to be a game of either-or, according to Dr. Isaac Bogoch, an infectious diseases specialist based out of Toronto General Hospital.
While it’s important to get older populations fully immunized, Bogoch said younger Canadians can still land in hospital and become very ill, and are more likely to be essential workers or influence community transmission.
“We should be able to continue to do the first-dose-based approach and provide second doses to vulnerable populations simultaneously,” he said.
“There’s individual protection and population-level protection. We can find that sweet spot where that Venn diagram overlaps.”
Moving timelines
Bogoch believes its likely that intervals will move up altogether based on the supply of shots coming into Canada.
Many provincial health authorities believe that too.
British Columbia says it is closely monitoring the supply of vaccines before making a firm call on accelerating the delivery of second shots. The province said it’s likely to happen sooner than expected, but they don’t expect a decision until early June.
In Ontario, Dr. Barbara Yaffe, the associate chief medical officer of health, said she doesn’t see the interval becoming “really short” but suggested it might end up shorter than the current 16 weeks.
It doesn’t mean the four-month interval plan is a bad one, however, said Bogoch. The U.K. has delivered one of the world’s fastest inoculation campaigns, which has focused on a one-shot strategy, helping to drastically reduce infection rates and deaths.
A recent study also backed up the delayed dosing plan. It found that the Pfizer vaccine could actually offer more protection in older people when a second dose was delayed about 12 weeks after the first.
Variants may also throw a wrench in the mix. The highly infectious B.1.617.2 variant, first identified in India, has prompted some parts of the U.K. to speed up second shots to boost protection.
The variant has been identified and designated as a “Variant of Concern” in Canada, though it is still being assessed to characterize its impact in the Canadian context.
“Variant or not, there’s a lot of reasons why we should try get second doses fast,” said Bogoch. “Variant or not, there’s also a lot of reasons why the first-dose-based approach in the context of limited resources is extremely important.”
Prioritizing and triaging who is eligible for a second dose will happen just as it did with initial vaccination campaigns, said Bogoch, and if we can shorten the duration for vulnerable populations “we certainly should.”
–With files from the Canadian Press and Global News’ Mike Le Couteur
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