OTTAWA — The National Advisory Committee on Immunization has expanded its recommended eligibility for booster shots of COVID-19 vaccines in response to reports of waning protection against the virus.
NACI now strongly recommends boosters for those over 50 and said all adults over the age of 18 may receive one as well.
The committee has also strengthened its recommendation for several other groups, and now strongly suggests boosters for people who received a full series of the Oxford-AstraZeneca or Janssen vaccine, those in or from First Nations, Inuit and Métis communities and front-line health workers.
The new recommendation was released after an urgent request from the federal government for information on the role of COVID-19 vaccine boosters in fighting the new Omicron variant, though NACI had already been working on updated advice.
Omicron came to light late last week, and has sparked tougher border measures around the world.
The World Health Organization has warned the high number of mutations could signal that it is more transmissible than previous strains.
Cases of Omicron have already cropped up across the country. Though most involve recent travel, one case, reported in Alberta, involved household transmission.
"We know that Canadians are asking increasingly about whether they should … receive boosters, and that question is obviously of greater importance now with the new variant," Health Minister Jean-Yves Duclos said in a press conference Tuesday.
NACI recommends people get an booster of an mRNA COVID-19 vaccine six months after their second shot.
NACI's analysis shows the vaccine offers waning protection against infection and transmission over time, and some studies show decreases in protection against serious infection, and more notably in older adults.
"The bottom line is that if there is waning immunity over time and an additional dose or boost to your immune system helps, at least in the short term, boost your antibody levels and increase the quality of your overall immune response and the durability of the response," said chief public health officer Dr. Theresa Tam at a briefing Friday.
There are already emerging indications that immunity is waning, according to Tam's deputy, Dr. Howard Njoo.
With highly transmissible variants like Delta and Omicron, NACI says breakthrough infections, particularly in communities with low vaccine coverage, can lead to high community rates of COVID-19.
"This can have significant impacts, especially on populations at high risk of COVID-19 illness and on health system capacity," NACI said in its report Friday.
Though these latest recommendations were only published Friday, many provinces have gone ahead with their own COVID-19 booster strategies and in some cases have pledged to offer them to any adult who wants one in coming weeks.
Provincial plans must also take into account their own demographics and health system capacity, and they have the difficult job of balancing those factors with the scientific evidence, said Tam.
"Everyone has been trying to focus on the groups at highest risk. And I hope that the NACI recommendation is very helpful to the provinces and territories, and I think begins to provide some guidance as to which age groups should receive the strongest focus," she said.
It's too early to say yet whether COVID-19 vaccine boosters will become a routine part of Canadian life in the months and years ahead, according to health officials. It's also possible that in the future people won't be considered fully vaccinated until they've received three vaccine doses.
Though clinical trials for booster shots did not include pregnant and breastfeeding women, they are also included in the recommendation.
NACI also favours Pfizer over Moderna when it comes to boosters for people 18 to 29 years old because of slightly higher instances in rare cases of heart inflammation associated with Moderna recipients in that age range.
Prime Minister Justin Trudeau said Wednesday when it comes to boosters, the priority is to follow NACI's advice on who should get them, and when, in light of the Omicron variant.
Vaccine supply will not be an issue, he said.
"We have lots of vaccines for boosters in Canada, we're receiving more into the new year. We are fine in terms of quantity. The issue is, what is the best recommendation for people to get those boosters and when," he said.
NACI did consider the ethical question of recommending boosters for healthy adults in Canada when the virus is running rampant in parts of the world where many high-risk people have yet to receive a first dose.
The World Health Organization has urged countries to delay boosters as long as possible, except for high-risk people, and to prioritize support for struggling nations instead.
"I think that that's what we're seeing in the advice today from the committee: an emphasis on those where the risk will be greatest and the need is greatest, and then also creating opportunities for others 18 to 49 years of age," said Matthew Tunis, executive secretary to NACI.
Tam said younger populations likely won't qualify for a booster until the new year under these recommendations anyways, because they will have to wait six months since they received their last dose.
This report by The Canadian Press was first published Dec. 3, 2021.
Laura Osman, The Canadian Press