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People walk into the Bill-Durnan COVID-19 vaccination site in Montreal, May 24, 2021, as the COVID-19 pandemic continues in Canada and around the world.Graham Hughes/The Canadian Press

Nathan Stall is a geriatrician at Sinai Health in Toronto and assistant scientific director of Ontario’s COVID-19 Science Advisory Table. Allison McGeer is an infectious diseases physician at Sinai Health in Toronto and a professor at the University of Toronto. Irfan Dhalla is a general internist and a vice-president at Unity Health Toronto, and an associate professor at the University of Toronto.

More than 20 million Canadian adults have received at least one dose of a COVID-19 vaccine. This is good news, reflecting an early and wise decision to extend the interval between first and second doses for most people to 16 weeks, in order to maximize the number of Canadians who would be protected from infection. This decision was supported by direct evidence from clinical trials, and mathematical modelling demonstrated that under conditions of a constrained vaccine supply, such an approach would save more lives than giving second doses more quickly. And indeed, the policy to delay second doses saved many lives.

But vaccine supply is now vastly improved, with Canada receiving 2- to 2.5-million doses of mRNA vaccines per week – enough to get first doses to 75 per cent of adults by the end of May and all adults by the end of June. Several provinces have started vaccinating adolescents. Yet only 1.7 million Canadians – mostly health care workers and those living in long-term care and retirement homes – have received both vaccine doses. With most adults partially vaccinated, our strategy must change, by circling back to older Canadians who have been waiting weeks or even months for their second doses, and rapidly immunizing them fully, even if first doses haven’t yet made their way into the arms of all Canadian adults and adolescents.

Older adults, after all, have borne the brunt of the pandemic. Despite accounting for just 12 per cent of the Canadian population, people over 70 have suffered more than 85 per cent of all COVID-19 deaths in the country.

One dose of an mRNA COVID-19 vaccine does provide substantial protection against symptomatic infection, even among older adults. But the immune response to vaccination is significantly lower in older adults, and effectiveness increases from 60 to 70 per cent with one dose to 85 to 90 per cent with two.

Consider 100 older adults who would become infected with COVID-19 without a vaccine. With one dose of a vaccine, about 35 people might become infected instead of 100; a second dose would reduce this number from 35 to about 12. The second dose is clearly still important. And because adults over 70 years of age who become infected with COVID-19 are 100 times more likely to die than adults aged 20-49, a second dose given to an older adult may prevent more serious illness and death than a first dose given to a younger adult.

Ontario data also show that COVID-19 infections among the partially vaccinated – those who are 14 or more days out from receiving one dose of a COVID-19 vaccine – are uncommon. A single dose provides good protection. However, uncommon does not mean never. Several dozen partially vaccinated Ontarians have died from a COVID-19 infection, and almost all of them were older than 70. Similar data in the United Kingdom have led that country to shorten the interval between vaccine doses to eight weeks for older adults and others who are at higher risk of dying from COVID-19.

The risk of death hasn’t been the only consequence for older Canadians during the pandemic. Older adults have not been able to see their families. Many have experienced fear and loneliness. Nearly one-third of all Canadians over the age of 65 reported that their mental health is worse now than before the pandemic. Providing second vaccine doses to older adults would help to liberate them from the profound isolation they have endured over the last 15 months.

To be clear, we are not questioning the life-saving decision to maximize first vaccine doses for all Canadians by extending second dose intervals. Nor are we questioning the need to continue providing first doses, including for younger Canadians.

What we are suggesting is that now is the time to start giving second doses of vaccine to adults who are 70 or older. Repeatedly, during the COVID-19 pandemic, we have overlooked the needs of older adults. Let’s not make that mistake again. Respecting our elders would mean fully vaccinating them, as quickly as possible.

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