Ontario will start administering third doses of COVID-19 vaccine to an additional 2.8 million people this month, including health-care workers and everyone over the age of 70, with a view to offering the general public booster shots sometime in 2022.

Starting on the morning of Nov. 6, people aged 70 and up, frontline healthcare workers, people who received two doses of the Astra Zeneca COVID-19 vaccine or other viral vector/adenovirus vaccines, and all Indigenous Ontarians will be able to start booking third shots.

Current Ontario guidelines allow for all residents of long-term care, First Nations elder care lodges and retirement homes to get a third dose.

They also allow third shots for a large number of immunocompromised people and others receiving immune system-suppressing drugs.

Of these eligible groups, 161,000 people or 65 per cent had received a third dose by Wednesday.

The widened eligibility this Saturday will now encompass about 1.7 million people over the age of 70, nearly 750,000 people working in healthcare, long-term care and other congregate settings and nearly 200,000 Indigenous Ontario residents.

It will also include roughly 200,000 people who received two doses of Astra Zeneca and those who received the Johnson & Johnson single shot vaccine in the United States and elsewhere.

Everyone in these four groups may receive a third shot no sooner than six months after their second shot.

The plan announced Wednesday calls for booster shot availability for the general public, gradually based on age and risk factors, starting sometime early in 2022.

“We are offering and suggesting that when it becomes available that all Ontarians consider taking this third dose, especially those who are vulnerable to this virus,” Chief Medical Officer of Health Dr. Kieran Moore said.

Officials speaking on background said they are awaiting further guidance from the federal National Advisory Committee on Immunization (NACI) but expect to be told to begin offering third shots to the general public in that timeframe, subject to changes in ongoing research on waning immunity.

“We wanted to signal that third doses will be part of our provincial strategy,” Moore said when asked about why Ontario’s plan already speaks of third doses for the general population when NACI hasn’t spoken about that yet.

They stressed that third shots of a COVID-19 vaccine will not be mandatory at this time, and the definition of fully vaccinated is not going to change for provincial mandate purposes.

“At five to seven months out from second dose, we are still seeing a good, profound and persistent level of protection at a population level - so we are not mandating any change in the validation or certification process within Ontario,” Moore said.

People will generally be eligible for a third shot no earlier than six months after receipt of their second shot.

The public will be offered mRNA vaccines for third shots only. But those under the age of 70 who get a third dose of the Moderna vaccine will be given a half shot – only 50 micrograms, compared to what was given to date.

Doctors said this is due to emerging research that smaller doses of the Moderna vaccine are as effective at generating lasting immunity.

“The 50 (microgram) dose is a very good dose as a booster in the general population of healthcare workers and has a very good safety profile,” Moore said. “But in the older population that has waning immunity, we thought it best to continue and the 100 (microgram) dose is best for that population.”

Moore also cautioned that emerging evidence suggested to him that COVID-19 will become endemic, like influenza.

“It is going to be persistent and will likely become an annual winter virus like the other coronaviruses,” he said.

Ontario health officials said there is a possibility of a combined influenza/COVID-19 booster, or some sort of fourth booster vaccine dose to become available in time for the 2022 flu season beginning in Oct. 2022, but everything is subject to shifting conclusions based on available research.

Ontario had 3.2 million doses of COVID-19 vaccine on hand as of Wednesday. This supply could expand easily as every dose of Moderna can now be halved for adults under the age of 70.

Ontario expecting a November approval for kids’ vaccine

Officials also said they are expecting Health Canada to approve the Pfizer-BioNTech vaccine for children aged 5-11 sometime this month, a day after the Public Health Agency of Canada sowed confusion online about how long it may take.

Moore said it is his expectation that the shot could be approved by Health Canada by the end of November.

The Ministry of Health said it does not expect any supply bottlenecks and hopes to launch children’s immunization campaigns across the province simultaneously, with no constraints such was what was seen in the spring 2021.

The province is preparing to immunize small children at existing mass immunization clinics, at or near schools and at pharmacies and pediatrician’s offices.

They plan to distribute consent to vaccinate forms to children at their schools for parents’ approval.