Fri. Jan 21st, 2022

With the news that Ontario is opening up to third doses of the COVID-19 vaccine for anyone aged 50 and over, many may be wondering if all two-shot Ontarians will need another jab.

In short, it’s likely – we just do not know when. It is also not clear whether a third dose will be considered necessary to be fully vaccinated or serve as a booster – and how it will be extended to those under 50 years of age.

What we do know is that research to date shows that those aged 50 and over – who are more prone to hospitalization and death if given COVID – benefit from a significant boost in protection with a third shot.

“Do we all need a third dose now? No. Do some of us need a third dose now? Yes. Should we extend the entitlement to third doses now? Yes, that’s what we do today,” said Dr. Isaac Bogoch, an infectious disease specialist at the University Health Network and a former member of Ontario’s now disbanded vaccine distribution task force.

“And more importantly, that entitlement can expand and should expand over time because it’s probably a three-dose vaccine for most adults. It probably is.”

Ontario’s Chief Medical Officer, Dr. Kieran Moore, announced Thursday that booster shots will be opened up to all adults 50 and over about six months or 168 days after their second dose.

They join the 70s and over, healthcare professionals and key caregivers in community settings, those who received two doses of the AstraZeneca vaccine or one dose of the Johnson & Johnson shot, as well as adults from First Nations, Inuit and Métis who are already justified.

An additional 250,000 immunocompromised people, transplant recipients, hematologic cancer patients, and seniors living in community settings were eligible to receive their boosters in late August.

Bookings for Ontarians 50 and above start on December 13, with dates for younger age groups in the new year. The extended eligibility for third doses comes as countries try to stay ahead of the new Omicron variant. But Moore said we will have to wait for new data to know how well boosters will protect against it.

Asked why he did not open up for third doses for everyone now – the US Centers for Disease Control and Prevention has recommended everyone 18 years and older get a third dose – he said that the priority for now is first doses for children and boosters for older adults.

“But we will definitely follow science,” he said.

A large Israeli study recently published in the Lancet showed that compared to two doses of the Pfizer COVID vaccine at least five months before, a third dose was about 93 percent effective in preventing hospitalization, 92 percent effective in preventing serious illness, and 81 percent . cents effective in preventing death, one week or more after the third dose.

“Our results suggest that a third dose of the (Pfizer) vaccine is effective in protecting individuals from severe COVID-19-related outcomes, compared to receiving only two doses at least five months ago,” the authors wrote.

Last month, the BMJ (formerly the British Medical Journal) reported that a preprint study by the UK Health Security Agency found “significantly increased protection” against a booster dose of symptomatic COVID for people over 50.

The journal noted that two weeks after receiving booster doses, protection for those receiving the Pfizer vaccine increased to 94 percent, while protection for those receiving AstraZeneca injections increased to 93.1 percent.

Closer to home, a recent report by Public Health Ontario on breakthrough cases or people receiving COVID despite being fully vaccinated found that the majority of those in need of hospital treatment are adults over the age of 60, with the highest share in the 80s.

Kelly Grindrod, a professor of pharmacy at the University of Waterloo, said while two doses still provide good protection, “one sees with declining immunity, hospitalizations in elderly populations.”

“So if and when we start seeing it with those under 50s, then we would know that this is also a third dose vaccine for young people,” she said.

Many vaccines take three doses, she added, so it would not be surprising if the COVID vaccines were found to need the same. Or people could require a booster every year, even every few years.

“This is not unusual … to give your immune system a vaccine and then remind it periodically how to fight something,” she said.

“Strengthening that memory is really, really helpful.”

Bogoch noted that new data from countries such as Israel, the United States and Qatar indicate signs of declining immunity over time, which may have resulted in some over-interpretation of the need for boosters. He said that even with this over-interpretation, however, there is clearly a need for third doses in some people.

He dampened his comments by pointing out that the new data on the need for boosters comes largely from countries that adhered to manufacturers’ recommended dose-to-dose ranges, such as Israel, which followed Pfizer’s instructions to administer the doses for three weeks. . part.

“In Canada, we did things a little differently. A lot of people got their first and second doses separated by two months and even more in some cases,” he said.

“What we know about multidose vaccines, including everything we’ve learned about the COVID-19 vaccine, is that you get more robust immunity by separating dose one and dose two.”

Dr. Jeff Kwong, a family physician and epidemiologist at the Dalla Lana School of Public Health, said when it comes to offering third doses to all age groups, “the writing is on the wall,” pointing to other jurisdictions, such as the United States, where adults at 18 years and over are already eligible, and British Columbia, which announced in the fall that they would start offering the third dose for all 12 years and over in January. “

“I think it’s just an inevitability,” he said.

Manitoba and the Northwest Territories have extended the third dose to all adults, while Nunavut recently made all 12 and up eligible.

“So far we’re framed it as two doses with a booster, but maybe it’s really three doses. For who knows what’s going to happen after the third dose? Nobody knows,” Kwong said. months after that? We have no idea. “


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