TORONTO — Ontario plans to eventually offer booster doses of COVID-19 vaccines to all residents, with the next priority group able to book appointments starting Saturday based on a higher risk of waning immunity.
There are 2.75 million people who will become eligible for boosters starting Nov. 6 – those aged 70 and older, health-care workers and essential caregivers in congregate settings, people who received two doses of the AstraZeneca vaccine or one dose of Janssen, and First Nations, Inuit and Metis adults and their non-Indigenous household members.
Ontario's chief medical officer of health said it's important to offer those people additional protection.
"These additional groups will benefit from a booster dose as they are at increased risk of waning immunity and greater risk of exposure, serious illness and outcomes," Dr. Kieran Moore said Wednesday.
Evidence suggests that immunity starts to wane after about six months, so those priority groups will be able to get their booster shots six months after their second dose.
Then, Ontario is eyeing early 2022 to expand booster doses to everyone else, based on a six-to-eight month interval after people received their second doses.
Ontario officials say the protection from two doses is still very high for the general population after six months, especially against severe illness and death, so a booster dose would provide additional protection against more mild illness.
The priority groups identified by Ontario are in line with recommendations from the National Advisory Committee on Immunization, though it said there's no evidence of widespread waning immunity against severe disease in the general population.
It's possible that one day three doses would be considered "fully vaccinated," Moore said, noting that he will follow the data on that.
Beyond that, health officials may need to consider a fourth dose if some new variant becomes a threat, Moore said.
"Never underestimate this virus," he said. "This virus wants to mutate. If it continues to change and the vaccine effectiveness goes down at a population level, we would have to entertain providing an additional dose of vaccine."
Ministry of health officials said that some pharmaceutical companies are working on combined COVID-flu vaccines and vaccines that are more specific to the Delta variant, so it's not unreasonable to expect there will be an additional booster in the future.
The province plans to focus on booster doses for now, but when the vaccine for kids aged five to 11 is approved - Moore said he expects that to come near the end of the month - the priority will shift to "the rapid provision of first doses for children."
All regions in the province are putting plans in place for the rollout of the vaccine for children, and provincial government officials say every public health unit will offer school-based clinics. Consent forms for parents or guardians to sign will be distributed through schools.
Other sites are expected to include mass immunization clinics, pharmacies, primary care doctors, mobile teams and children's hospitals.
More than 250,000 people in Ontario are already eligible for third doses, including certain immunocompromised people and residents of long-term care, retirement homes and other seniors' congregate settings. Officials say 65 per cent of those already eligible have had a third dose. Either mRNA vaccine can be used for a booster dose, officials say.
Newly eligible residents can book boosters starting Saturday at 8 a.m. through the provincial portal or phone line, public health units that have their own booking systems, and select pharmacies. Hospital-based health workers should contact their hospital employer.
This report by The Canadian Press was first published Nov. 3, 2021.
Allison Jones, The Canadian Press