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COVID-19 booster shots: Will you need more than one?

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Since the first cases of Omicron were reported in Canada just a few weeks ago, infections with the new COVID-19 variant have skyrocketed across the country. On Dec. 13 alone, public health authorities estimated that of daily new infections in Ontario .

Earlier this month, Canada鈥檚 National Advisory Committee on Immunization that booster shots be administered to Canadians aged 50 and older, as well as other at-risk groups. While each province and territory has enacted its own policies on booster eligibility, third doses are being offered in varying degrees across the country.

With such a strong emphasis on booster shots, is it possible Canadians may need a fourth vaccine dose for ongoing protection against COVID-19?

According to Dr. Brian Conway, an infectious disease expert and medical director of the Vancouver Infectious Diseases Centre, it鈥檚 too early to say whether a fourth dose might be needed any time soon. Still, he said it鈥檚 likely that an annual booster shot will be necessary to strengthen the body鈥檚 immune response, something he anticipates will be seen in the fall to coincide with flu season.

鈥淚 think it's premature to conclude that that will be needed in the short to medium term,鈥 Conway told CTVNews.ca in a phone interview on Wednesday. 鈥淏ut that's what I'm really seeing 鈥 a yearly COVID shot along with the flu shot, and COVID will become more manageable.鈥

A lot of this depends on the efficacy of these vaccines, Conway said, particularly against Omicron. Earlier this year, both and  reported strong effectiveness in their vaccines until about four to six months after they鈥檝e been administered. But it remains to be seen just how successful booster shots will be in fighting off the new variant, and for how long.

鈥淭his is a bit of a moving target,鈥 Conway said. 鈥淲e've now realized that Omicron is going to take over the epidemic, and that vaccine protection against Omicron is probably significantly less over time.鈥

Some of this uncertainty is reflected in the different timelines for booster eligibility implemented across provinces and territories. Starting in January 2022, for example, adults in British Columbia will be eligible for their booster shot six to eight months after getting their primary series. Meanwhile, in Ontario, the minimum interval was recently lowered to just three months, or 84 days.

But it鈥檚 really only after people have gotten their third dose that experts can assess its efficacy against Omicron and decide when a fourth shot might be needed, Conway said. Still, he foresees annual booster shots being given out in the fall.

鈥淭he question of whether the fourth shot will be needed before next fall, we will be able to answer in February or March, depending on how the epidemic evolves,鈥 he explained. 鈥淢eaning if we're seeing more cases, especially among triply vaccinated individuals, then it is at that point that we will decide if a fourth shot is needed before next fall.鈥

COULD WE SEE A COVID-19 AND FLU VACCINE?

According to Conway, the COVID-19 pandemic is evolving similarly to the previous influenza pandemic, spreading in waves before it transformed into an endemic virus. He also pointed to a resemblance in the ways they鈥檙e transmitted, namely through person-to-person contact with the containing the virus through coughing or sneezing.

鈥淭he similarity of the seasonality and the modes of transmission speak to me, as they will both become endemic and require yearly shots,鈥 he said.

Moderna also appears to be gravitating towards the idea of an annual booster shot. The pharmaceutical company recently announced it is working with Novavax on a single-dose vaccine that combines a COVID-19 booster shot with an experimental flu shot. The vaccine has since begun clinical trails.

鈥淭hey鈥檝e made up their minds that there will likely be yearly COVID shots,鈥 said Conway. 鈥淏ig Pharma doesn't invest money in developing a product unless they think there will be a market for it.鈥

Based on a published by the British Medical Journal, researchers discovered it was safe to administer a second dose of the COVID-19 vaccine and a flu vaccine at the same time, as long as they were given in different arms. The study also showed that doing so did not affect the immune response to either vaccine. The study was recently published as a preprint and is yet to complete peer review.

Still, experts insist more time is necessary to evaluate the situation. Last weekend, Dr. Anthony Fauci, the United States鈥 top infectious disease expert, stated that while he isn鈥檛 ruling out the possibility of annual booster shots in the future, it鈥檚 too early to determine whether they鈥檙e needed.

鈥淚t's tough to tell,鈥 he said in the interview that aired on ABC News. 鈥淵ou don't know that鈥ntil you just follow it over a period of months.鈥

Earlier this month, Dr. Matthew Miller, an associate professor at McMaster University鈥檚 department of biochemistry and biomedical sciences, said this question 鈥渟till requires pretty intensive investigation.

鈥淥n one hand, it鈥檚 a decision that鈥檚 going to be impacted by how long we see immunity last,鈥 he explained. 鈥淏ut that鈥檚 also related to how much the virus is circulating [and] how much the virus is evolving.鈥

Conway鈥檚 best advice for now?

鈥淕o get your third shot as soon as you're eligible for it, and stay tuned.鈥

Do you have questions about the Omicron COVID-19 variant? We want to hear from you.

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