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Third COVID-19 vaccine doses: Who is eligible in Ontario and how can they get one?

As Ontario edges closer to its goal of having 90 per cent of eligible residents fully vaccinated, the Ministry of Health (MOH) has been administering third doses to select populations.

The Ministry is underlining that two doses represent a complete vaccine series and provide strong protection against the virus, including the Delta variant, but are also advising that “for some populations, a third dose may be required as two doses may not provide sufficient protection.”

As of Thursday, Ontario residents over the age of 50 can book an appointment to get their third dose.

Ontarians must wait at least six months after they get their second dose to get the booster.

According to the most recent data, just under 80 per cent of eligible Ontarians have received two doses of a COVID-19 vaccine.

The CEO of Ontario's Pharmacists Association said Thursday morning that he would recommend opening up eligibility to all age groups, while still adhering to the recommended six-month timeline.

"That will allow us to do this in a staggered fashion, manage the demand and supply and make sure everybody has optimal immunity and efficacy of the vaccines against the variants because the immunity does wane after six months. We know that from the current data and that's why boosters are going to be so important."

However, Ontario's Chief Medical Officer of Health Dr. Kieran Moore said the province wants to ensure it has the capacity to offer booster shots along with vaccinated children prior to removing all age restrictions.

"I really want the over 70s in particular to come forward as we know they're most at risk of fading immunity and a risk for transmission. In these next 10 days you will be well protected for the holiday season and children will get the maximum benefit of being immunized in the next 10 days for the holiday season as well." Moore said.

The government has said that booster shots would be available gradually to the general public based on age and risk factors starting in early 2022.

Officials say that more than 696,000 third doses have been administered in Ontario so far.


Residents over the age of 50

As announced on Thursday, individuals in this age group will be able to book their appointments starting at 8 a.m. on Dec. 13.

The moderate-to-severely immunocompromised population

According to the Ministry of Health, populations that have demonstrated a suboptimal immune response to a complete two-dose COVID-19 vaccine series due to their underlying condition are eligible to receive a third dose of the vaccine.

This includes:

  • Individuals receiving active treatment (e.g., chemotherapy, targeted therapies, immunotherapy) for solid tumour or hematologic malignancies.
  • Recipients of solid-organ transplant and taking immunosuppressive therapy 1Active treatment includes patients who have completed treat
  • Recipients of chimeric antigen receptor (CAR)-T-cell therapy or hematopoietic stem cell transplant (within 2 years of transplantation or taking immunosuppression therapy).
  • Individuals with moderate to severe primary immunodeficiency.
  • Individuals with stage 3 or advanced untreated HIV infection and those with acquired immunodeficiency syndrome.
  • Individuals receiving active treatment with the following categories of immunosuppressive therapies: anti-B cell therapies, high-dose systemic corticosteroids, alkylating agents, antimetabolites, or tumour-necrosis factor (TNF) inhibitors and other biologic agents that are significantly immunosuppressive.
  • Individuals receiving dialysis, as long as it’s been at least 56 days since their second shot.

A full list of immunosuppressant medications that render patients eligible for third doses provided by the Ministry can be found here.

Seniors in congregate settings

This includes residents of long-term care homes, retirement homes, elder care lodges, and elderly living in other congregate settings, such as assisted-living facilities, chronic care hospitals and “naturally occurring” congregate retirement settings/congregate seniors apartment buildings, the Ministry said.

Because this subgroup was prioritized when vaccines were first authorized and many completed their vaccination series early, the Ministry states that there has been “more time for waning [efficacy.]”

“Vaccines have been effective against COVID-19 in long-term care homes in the 3-4 months after vaccination, but outbreaks are still occurring,” the Ministry said. “In these outbreaks, fully vaccinated residents are being infected, and in some instances leading to severe illness and death.”

“Offering a third dose of a COVID-19 vaccine to this population is intended to help increase protection and prevent outbreaks among this vulnerable population.”


Of the eligible populations, there are a few exceptions.

According to the Ministry, individuals who have experienced myocarditis or pericarditis following any dose of an mRNA vaccine should defer receiving a third mRNA dose until more information is available.

Individuals who received AstraZeneca/COVISHIELD COVID-19 for their first or second dose will still be eligible to receive a third dose, but it is recommended by the Ministry that the third dose be an mRNA vaccine, unless advised otherwise by a medical professional.


If eligible, residents can obtain their third dose of a COVID-19 vaccine through largely the same avenues that they received their first or second — through the provincial booking system or call centre, at a pharmacy, hospital or primary care provider.

“If you are eligible for a booster dose of the COVID-19 vaccine, please book your appointment as soon as you can to provide yourself with an extra layer of protection,” Moore said. Top Stories

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