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The National Advisory Committee on Immunization is now strongly recommending that people 50 and older receive a booster shot at least six months after their second dose.Paul Chiasson/The Canadian Press

Canadians 18 and older may receive a booster shot of an mRNA vaccine at least six months after their second dose, the country’s expert vaccine panel says in new guidance aimed at tackling growing COVID-19 case counts in parts of the country and concerns about the new, possibly more transmissible Omicron variant.

The National Advisory Committee on Immunization, a federal panel that provides advice to provinces on new vaccines, is now strongly recommending that people 50 and older receive a booster shot at least six months after their second dose. The strong recommendation also applies to adults living in long-term care or other congregate settings, people who received two doses of the AstraZeneca vaccine or the single-dose Janssen (Johnson & Johnson) viral-vector vaccines, adults in First Nations, Inuit or Métis communities, as well as all frontline health care workers.

NACI also said people 18 to 49 may receive a booster shot depending on a variety of risk factors, such as local transmission rates, evidence of waning immunity or a medical condition that may increase a person’s risk of severe illness. While people who are pregnant or breastfeeding weren’t included in clinical trials of booster shots, NACI said the evidence shows mRNA vaccines are safe in those individuals. Given the risk of severe illness tied to pregnancy, people who are pregnant or breastfeeding should be offered a third dose, NACI said.

It’s unclear what role the Omicron variant will play in the coming months. There is evidence the variant is more transmissible than Delta and may evade some vaccine protection, which could lead to higher case counts and more hospitalizations and deaths.

Many experts say existing vaccines should continue to offer good or partial protection against Omicron and that booster shots will likely help.

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While many are concerned about the possible risk posed by the new variant, health leaders in Canada say the dominant Delta variant poses an immediate threat, which is a major reason behind the growing push for expanded booster eligibility.

“Right now, we have the potential for a Delta surge,” Chief Public Health Officer Theresa Tam said in a briefing Friday.

In Ontario, for instance, new daily COVID-19 cases exceeded 1,000 Friday for the first time since May.

Earlier this week, Ontario and Alberta announced they would expand eligibility for booster shots in order to protect against possible new waves of COVID-19. Ontario will let people 50 and older sign up for a booster shot as of mid-December, while Alberta has started letting people 60 and older sign up. Quebec Premier François Legault said this week the province won’t offer booster shots to anyone under 70 yet.

The arrival of the anticipated NACI guidance on boosters could change that, as provinces typically look to NACI to help set vaccine administration policy.

Health experts say provinces should be doing more to prepare for an expected surge in cases over the coming months, as more people gather indoors and with public-health restrictions relaxed in many places. Officials may want to consider imposing some reduced capacity limits and doing more to improve vaccine and booster-shot uptake, experts say.

There is also a growing push to make COVID-19 treatments more readily available. The federal government announced Friday that it has agreements with two pharmaceutical companies to purchase their new anti-viral drugs, which have been shown in trials to reduce a person’s risk of developing severe illness as a result of COVID-19. The pills are under review by Health Canada.

The mRNA vaccines have been tied to a small risk of myocarditis and pericarditis – heart inflammation – particularly in young men, after a second dose of the Moderna vaccine. The new NACI recommendations say that in order to reduce those risks, people 12 to 29 should be offered the Pfizer/BioNTech vaccine as first and second doses with an eight-week interval between the doses. People 18 to 29 should be offered a booster shot of the Pfizer/BioNTech vaccine (booster shots are not authorized for people under 18), the recommendations also say.

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