A U.S. proposal to make COVID-19 vaccinations an annual shot could increase booster uptake if a similar policy were adopted in Canada, but it may be too early to make such a move, according to some health experts.
SARS‑CoV‑2 has yet to move into predictable or seasonal patterns of infection, and immunity gained from the virus — whether through vaccination or illness — wanes over time, according to numerous scientific studies.
This makes the question of how often COVID-19 vaccinations should be repeated a challenging one to answer, Dr. Joachim Hombach, executive secretary of the WHO Strategic Advisory Group of Experts on Immunization (SAGE), said during a briefing earlier this week.
“I don’t think we have, for the time being, definitive answers,” he said.
“We all want to come to simplified vaccination recommendations and also vaccination recommendations that we can plan ahead … but we still live with very significant uncertainties.”
On Thursday, the U.S. Food and Drug Administration (FDA) asked its scientific advisors to consider simplifying COVID-19 vaccination to encourage most adults and children to get a once-a-year shot to protect against the virus.
Under this proposal, Americans would no longer have to keep track of how many shots they’ve received or how many months it’s been since their last booster.
Following a meeting on Thursday, the advisory panel mostly agreed with the FDA’s annual booster proposal, however, there was some debate about whether certain populations should get two doses a year.
Several members of the advisory group asked for more robust data on the benefits of annual shots for younger, healthier people, leaving the question of whether the U.S. will adopt annual COVID-19 boosters unclear.
Canadian health officials have not indicated whether they are considering a similar proposal, but in a statement to Global News, Health Canada said the National Advisory Committee on Immunization (NACI) “continues to monitor evolving evidence, including evidence on the potential need or benefit of booster shots, and will update recommendations as required.”
Updated guidance issued by NACI last week reinforced earlier advice that all Canadians adults and at-risk teens over 12 should receive at least one booster dose of the COVID-19 vaccine.
It further advised that all Canadians over the age of five who are immunocompromised or those at risk of severe health complications from the virus should have received a booster since the start of fall 2022.
Recommended intervals between doses in Canada are six months, with shorter intervals of as little as three months for those at heightened epidemiologic risk.
If Canada were to move instead to recommended yearly boosters, this would be a “reasonable” proposal, given the current state of the pandemic, says Earl Brown, a professor emeritus of virology at the University of Ottawa.
“It may be a bit premature, but the essence of the proposal isn’t that different from what we’re doing right now,” he said.
Currently, Canada is trying to keep up with the changing nature of the virus with vaccines that, while imperfect, do offer protection against severe illness and death, including updated vaccines that also protect against Omicron variants BA.4 and BA.5, he said.
“So, it may be a bit premature to say we’re in sort of a status quo, but we are able to manage what the virus is coming at us with our existing vaccination tools.”
Horacio Bach, a clinical adjunct professor of infectious diseases at the University of British Columbia, says he believes moving to an annual COVID-19 booster could help increase the number of Canadians getting booster doses.
“I think it’s a great move because no matter what, we will need to have these boosters every year, probably, as we do with the flu,” he said.
He pointed to federal data showing only 25 per cent of Canadians have received a COVID-19 booster in the last six months.
Some of this low uptake may be due to vaccine fatigue among many Canadians, the vast majority of whom have received their first two doses of the COVID-19 shot, he said.
Making it annual, perhaps even combining it with the annual flu shot, could address fatigue while still ensuring a critical mass of Canadians maintains immunity against the virus, Bach said.
However, some populations, such as elder Canadians and those who are immunocompromised, may continue to need at least two shots a year, he added.
“But for the general population, at least one a year,” he said.
Dr. Catherine Hankins, an epidemiologist, professor and interim chair in the department of global and public health at McGill University, says while she understands the U.S. may be trying to increase COVID-19 booster uptake with its proposal, she believes it may be too early for Canada to consider moving to an annual booster.
She also expressed concern over the potential that making such a move could promote the idea among the public that COVID-19 is no longer a threat, or that “COVID is over,” as some — including U.S. President Joe Biden — have controversially declared in recent months.
“COVID is definitely not over, unfortunately. We feel like we’re done with it, but it’s not done with us. In fact, we’re seeing a large number of cases happening elsewhere in the world right now,” she said.
While much of the Canadian population has developed strong levels of immunity against the virus, including boosted immunity due to high levels of ‘hybrid immunity’ garnered through a combination of vaccination and infection, this immunity wanes over time, which throws a wrench in the discussion of reducing the frequency of booster doses, Hankins said.
“This virus is developing into more immune-evasive, more transmissible variants that become dominant, and therefore we’re confronted again by another type that we don’t quite recognize,” she said.
“If you could have an annual combined COVID/flu vaccine, that would be a lot easier for people. But it’s not clear that that would keep you well protected from COVID during the rest of the year.”
— with a file from The Associated Press