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Kieran Moore, Ontario’s Chief Medical Officer of Health, said it remains “absolutely unclear” as to how effective the shots are against the new Omicron variant – although he said he expects at least some level of protection.Chris Young/The Canadian Press

Ontario will expand third doses of COVID-19 booster shots to people 50 and over starting on Dec. 13, as it looks to stave off the threat of rising case counts and the new Omicron variant, the province’s top doctor said Thursday.

Still, Kieran Moore, Ontario’s Chief Medical Officer of Health, said it remains “absolutely unclear” as to how effective the shots are against the new variant – although he said he expects at least some level of protection.

“We don’t expect 100 per cent loss of the efficacy of the vaccine against Omicron,” Dr. Moore said Thursday.

“I do hope and wish that it gives us also protection against Omicron but I have to be completely honest that we don’t have the science to make that statement yet.”

Dr. Moore said the province will monitor booster shot uptake before further opening it up to additional groups in the new year, so as not to overwhelm the health system, which is also issuing flu shots and immunizing children at the same time. The expansion announced Thursday means 4.6 million more Ontarians will be eligible for a booster, for a total of 5.7 million people soon to be eligible for a third shot.

Meanwhile, the province has confirmed a fifth case of the Omicron coronavirus variant, in the Durham Region, in addition to four cases already found in Ottawa. Dr. Moore said he expects more cases, and outbreaks, to be detected in Ontario, with 1,800 people now in isolation across Canada after returning from one of the 10 countries that are under strict federal travel restrictions.

He said the current Omicron cases in Ontario are a mix of unvaccinated and vaccinated people from different flights, and the province continues to monitor the variant’s transmissibility, its severity and its impact on the vaccine’s effectiveness.

Toronto Public Health on Thursday also declared an Omicron-driven outbreak at the Toronto East Detention Centre, with one confirmed COVID-19 case of a staff member, followed by four inmates. Later on Thursday, Halton Region said it had identified one lab-confirmed and two probable cases of the Omicron variant, linked to recent travel to Nigeria.

The expanded booster eligibility takes effect on Dec. 13 at 8 a.m. ET, when people 50 and over will be able to book shots through Ontario’s online booking system, by phone, through local public-health units or in pharmacies and doctor offices. People must wait 168 days, or approximately six months, since their second shots to receive boosters.

In addition, those receiving dialysis treatments are immediately eligible for third doses if it has been 56 days since their second shot. The province now also recommends that people receiving cell treatments following therapy or a transplant get vaccinated again with both shots because of lost immunity.

Starting in January, the province also expects to expand eligibility to more people “based on age and risk,” with an interval of between six to eight months since the second dose.

But Dr. Moore said Ontario won’t follow the footsteps of the U.S. Centers for Disease Control and Prevention, which has recommended third shots for all adults 18 and over. He said those under 50 are still showing strong immunity against the Delta variant, the dominant strain in Ontario.

“We don’t want to overwhelm a finite system,” he said.

Isaac Bogoch, an infectious-diseases physician at Toronto’s University Health Network who previously sat on the province’s vaccine task force, called Ontario’s booster plan “reasonable” and said it could always be altered if circumstances change.

“There will be a gradual expansion probably over the next month or two,” he said. “Not everybody would need a third dose today.”

Ontario also announced that it would start giving out “a limited supply” of the single-dose Johnson & Johnson vaccine, effective immediately. The Johnson & Johnson vaccine will be available to those 18 and over “who have an allergy or contraindication” to the mRNA vaccines by Pfizer and Moderna, or people who request it and have not yet been vaccinated.

The province is also preparing a strategy for COVID-19 treatments, when approved, such as molnupiravir, an oral treatment for high-risk unvaccinated patients with mild to moderate COVID-19.

Currently in Ontario, booster shots are limited to those 70 and over, people who have received two doses of the AstraZeneca vaccine, health care workers and essential caregivers, and Indigenous populations. To date, about 20 per cent of those 70 and over have received their third dose.

Canada’s National Advisory Committee on Immunization is also expected to announce new recommendations on Friday for booster shots for anyone 50 and older.

So far in Ontario, 90 per cent of those 12 and over have received one dose, and 87.2 per cent have received their second dose, while 12.3 per cent of children 5 to 11 have now had a shot. Dr. Moore said he would be “disappointed” if Ontario didn’t immunize 50 per cent of the five- to 11-year-olds with one dose before the new year.

With a report from Carly Weeks in Toronto

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