Updated COVID-19 vaccines recommended for fall boosters, Canada's vaccine advisers say

The country's national vaccine advisers are recommendingCanadians get another COVID-19 booster shot this fall, with updated vaccines expected in the months ahead.

The next round of vaccines will likely be monovalent meaning they will specifically target the Omicron family of sub-lineagesthat are still circulating globally, the National Advisory Committee on Immunization (NACI) said Tuesday.

"An additional dose using the latest vaccine formulations will be an important tool to not only build back protection against severe disease that wanes over time, but also protect against currently circulating SARS-CoV-2 variants," Canada's chief public health officer, Dr. Theresa Tam, said in a statement.

"This additional dose is especially important for those at increased risk of COVID-19 infection or severe disease."

Back in May, a World Health Organization advisory group suggested it would be ideal to focus on a monovalent shot targeting XBB.1 and its offshoots, rather than a bivalent vaccine targeting both new and old strains of the coronavirus, which was the boosterlast rolled out in Canada.

"Manufacturers have indicated that new COVID-19 vaccine formulations are in development and products are forthcoming," Canada's vaccine advisers wrote, adding that booster doses expected for the fall will be "updated to target more recent, immune-evasive SARS-CoV-2 variants."

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The mRNA-based vaccines remain the preferred COVID-19 vaccine product, the recommendations continued.

Dr. Allison McGeer,an infectious disease specialistat Mount Sinai Hospital in Toronto, says the recommendations from NACIwere expected.

"People have thought really carefully about ...what's going to give us the best protection."

But McGeer said this advice could still change depending on the disease trajectory, level of infection and whether any newstrains arise in the next few months.

Who should get vaccinated and when?

NACI's new guidance states that Canadians should wait to get a booster at least six months after a previous vaccine dose or a known SARS-CoV-2 infection whichever came later. That's because research suggests the shots are more effective when they're spaced out from an active infection or prior vaccination, as CBC News has previously reported.

One Canadian study, for instance, suggests protection against infection from two doses of the Pfizer vaccine spikes when the first and second shots are spread out, from roughly 80 per cent after a few weeksto more than 90 per cent after four months.

While NACI advises that everyone should get a dose of a new vaccine, it specifically advises that people at a higher risk of severe disease get the booster dose.

Vulnerable groups at higher risk include:

• Adults 65 years and older.
• Long-term care and congregate living residents.
• People with underlying medical conditions that put them at higher risk of severe disease.
• People who are pregnant.
• First Nations, Mtis and Inuit people.
• People from racialized and other equity-deserving communities.
• People who provide essential community services.

Dr. Isaac Bogoch, an infectious diseases specialist with the University Health Network in Toronto, agreed that ongoing vaccination remains essential for those at-risk groups.

"The challenge is: What does everyone else do? It's clear who's at risk of greater infection but what do you do for everybody else?" he said.

"One of the challenges that's going to be faced is uptake of vaccination in the other groups. Are people going to be coming out for that booster vaccine?"

More targeted communication strategies will be useful going forward to reach people of varying risk levels, Bogoch added.

Federal figuresshow the vast majority of Canadians have been vaccinated against COVID-19 so far, with more than 80 per cent of the population completing their primary shots. But interest in getting additional shots has dropped over time with less than six per cent of Canadians receiving a booster dose, or completing their primary series, within the last six months.

Protection from vaccination, infection decreases'over time'

NACI continues to recommend COVID-19 vaccination for anyone who hasn't yet been immunized, including individuals older than fiveand children six months to five years of age. The currently available bivalent vaccines can be used for a primary vaccine series for either age group, the advisers noted.

NACI also noted the higher levels of protection against severe disease provided by hybrid immunity when people have been both vaccinated and previously infected as opposed to just vaccination or a prior infection alone.

"For this reason, an additional dose of vaccine starting this fall is particularly important for those who have not been previously infected and have protection from vaccination alone," the guidance said.

"However, even with hybrid immunity, protection against infection will decrease over time and the duration of protection against severe disease varies between studies and is unknown in the context of currently circulating variants."

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While people might be fatigued with getting COVID-19 shots, McGeer saidit's important to remember that "you will be less likely to get ill and less likely to dieif you choose to get vaccinated."

When it comes to whether newCOVID-19 vaccinations will continue to be offered year after year, similar to the flu, McGeer said it's "too early to tell."

Is another wave coming?

While it's unclear whether Canada will see an increase in COVID-19 cases come the fall, NACI says that it's usually a time when other respiratory illnesses are on the rise, like the flu and RSV.

"We know there's going to be more COVID on the horizon in the fall and winter months," Bogoch said.

As a result, NACI advises that people get vaccinated to protect those who are vulnerable to other illnesses and to prevent the health-care system from becoming overwhelmed.

In the latest recommendations, the committee says that modelling predicts a fall vaccination dose could "prevent thousands of hospitalizations and deaths across the country" over the next year.

It's unclear when exactly the new doses will be made available, but NACI says that it will continue to review the latest information on the vaccine and provide updated recommendations as needed.