TORONTO -- The availability of booster shots and third doses of COVID-19 vaccines is a hot topic for many Canadians as additional doses are being rolled out for certain populations or those who need to travel for work, depending on their province or territory of residence.

Health experts and federal agencies have been debating the need for booster shots across the general population, saying that a primary vaccine course still provides good protection against COVID-19.

Health Canada regulates drugs and vaccines in this country, while the National Advisory Committee on Immunization (NACI) is the federal entity that provides advice to provinces and territories regarding use of the COVID-19 vaccines.

On Nov. 12, Health Canada approved the use of the Moderna COVID-19 vaccine for booster shots in people aged 18 and up, to be given at least six months after finishing a primary vaccine course. The boosters contain a half-dose of the Moderna vaccine.

Health Canada on Nov. 9 authorized use of the Pfizer-BioNTech COVID-19 vaccine as a booster for all people 18 and older, to be administered at least six months after completing a primary vaccine course. These boosters contain a full dose of the Pfizer vaccine.

NACI suggested on Oct. 29 that provinces offer mRNA vaccine booster shots to Canadians who are aged 70 and up, along with people who received two doses of the AstraZeneca vaccine or one dose of the Janssen vaccine and adults in First Nations, Inuit and Metis communities, at least six months after their primary vaccine course.

Front-line health-care workers who have direct in-person contact with patients and who were originally vaccinated within a short time interval are also recommended for boosters.

In late September, NACI recommended booster shots for all long-term care residents and seniors living in other congregate settings at least six months after the primary vaccine course.

A few weeks earlier, NACI recommended third vaccine doses be administered to certain immunocompromised individuals at least 28 days after their previous dose. Each province and territory has enacted a third-dose policy for immunocompromised people.

Third doses are considered part of a primary vaccine course, while boosters are meant to be given when vaccine effectiveness wanes and often, but not always, contain a smaller dosage.

Public opinion on the matter appears to sway in favour of booster shots. The vast majority of Canadians have expressed interest in one, according to a survey commissioned by CTV News, with 69 per cent of respondents saying they were interested and 15 per cent saying they were somewhat interested.

ELIGIBILITY FOR ADDITIONAL DOSES BY PROVINCE AND TERRITORY

British Columbia: Seniors aged 70 and up and Indigenous people aged 18 and up, as well as those who live in rural and remote Indigenous communities, are able to get an mRNA booster shot. Residents of independent living facilities or people who receive long-term home support are also eligible. Health-care workers who received their first two COVID-19 vaccine doses on a shortened schedule, that is, less than 42 days between doses, can also get boosters. Starting in January 2022, everyone aged 18 and up will be invited to get boosters between six and eight months after their primary vaccine course. Those who received two doses of the AstraZeneca vaccine will only have to wait six months. People who are moderately to severely immunocompromised may be able get a third dose four weeks after their second one. Booking invites will be sent through the province's Get Vaccinated system.

Alberta: Those who are eligible for an additional dose include Albertans aged 75 and up at least six months after receiving their second dose. First Nations, Inuit and Métis people aged 65 and up can also receive a third shot six months after their second dose. Immunocompromised individuals 12 years and older with specific conditions may be eligible for a third dose eight weeks after their second one. Residents of seniors' supportive living facilities can get a third shot five months after their second one. Finally, travellers to places where the AstraZeneca vaccine or mixed doses aren't recognized can get a third shot four weeks after their second dose.

Saskatchewan: Residents 65 years and older, health-care workers and individuals born in 2009 or earlier with certain underlying health conditions, can receive an mRNA booster dose six months following their second dose. Residents of the Far North and those living in First Nations communities who are aged 50 and older may also get boosters. Some immunocompromised and clinically extremely vulnerable individuals can receive a third dose 28 days after their second one. Those who are eligible for medical reasons will receive a letter from the ministry of health or their physician. A third or even fourth dose is also available for those who may require it for international travel.

Manitoba: Manitoba is allowing all adults 18 and older to receive a COVID-19 booster shot a minimum of six months after a second dose. The province also recommends an additional mRNA vaccine dose for residents of personal care homes or congregate elderly person housing, pregnant people and individuals living north of the 53rd parallel or in a remote community, as well as First Nations, Inuit and Métis people. Manitobans who have only received a viral vector COVID-19 vaccine or one not approved by Health Canada, people who work or live in a congregate living facility and individuals receiving home care or any level of Community Living Disability Service support, as well as health-care workers who have direct contact with patients, personal care home residents or clients, are also recommended to get an additional dose. A third dose is also recommended for people who may be immunocompromised.

Ontario: A third dose is currently recommended for people who may be moderately to severely immunocompromised, eight weeks after their previous dose. Residents of long-term care homes, high-risk retirement homes, First Nations elder care lodges and elderly people living in other congregate settings may also be able to get an additional dose five months after their second one. Residents over the age of 70, health-care workers and designated essential caregivers in congregate settings, First Nation, Inuit, and Metis adults and their non-Indigenous household members are eligible as long as they received their second dose at least six months ago. Individuals who received a complete series of a viral vector vaccine (i.e. two doses of AstraZeneca or one dose of Janssen) at least six months ago are also eligible. In a similar category, individuals with proof of immunization who underwent a one- or two-dose course of a COVID-19 vaccine not approved by Health Canada may receive an additional mRNA vaccine dose at least 28 days after the preceding one.The province says by early 2022, everyone aged 12 and older who received their second dose six to eight months ago will be able to receive their third shot, pending clinical recommendation.

Quebec: An optional booster shot is now available to people aged 70 and older in Quebec. People 12 and older who are immunocompromised or on dialysis are also eligible to receive their third dose. Beginning Nov. 25, people who have received two doses of AstraZeneca or the Covishield vaccines will be eligible to schedule an appointment for a third dose. An mRNA vaccine booster dose is recommended for residents of residential and long-term care centres, people living in private seniors residences and people living in settings with a high percentage of vulnerable older adults, such as intermediate and family-type resources, as well as certain religious communities. Boosters should be administered six months after the primary vaccine course, however, a minimum delay of five months is acceptable for those who wish to receive a flu shot at the same time. For people on dialysis and certain individuals with weakened immune systems, a third COVID-19 vaccine dose is recommended four weeks after the second dose.

New Brunswick: Individuals who are immunocompromised or those who have complex medical conditions are now eligible to get athird dose of a COVID-19 vaccine. Residents of nursing homes and other adult residential facilities can also book their appointments.

Health care workers, First Nations individuals and those 65 and older who received their second dose of an mRNA COVID-19 vaccine at least six months ago are also eligible for a booster.

People who have received one or two doses of the AstraZeneca vaccine, regardless of their age can also get their booster shot, as long as 28 days have passed since their second dose.

Nova Scotia: Seniors aged 70 or older are now eligible to receive their COVID-19booster shot. Long-term care home residents who have received two doses of a COVID-19 vaccineat least six months ago are eligible. Additionally, designated caregivers of long-term care residents and frontline health care workers who have two doses of a COVID-19 vaccine, with less than 28 days between doses, are eligible for a third shot. Anyone who received two doses of the AstraZeneca vaccine, can also book their third dose.

Members of First Nations or African Nova Scotian communities who are 30 or older can also receive their booster shot. Moderately or severely immunocompromised people who received two doses of a COVID-19 vaccine can also get a booster dose of an mRNA shot at least 28 days after they received their last dose. An additional mRNA dose is also available for those who are required to travel for work and need the extra shot to meet travel or self-isolation requirements in another country.

Prince Edward Island: Residents of long-term care and community care facilities, seniors aged 70 and up and Indigenous people, as well as individuals aged 18 and up who received two doses of the AstraZeneca vaccine or one dose of the Johnson and Johnson vaccine, are recommended for an additional dose at least six months after their initial vaccine course and are eligible to receive one. Health-care workers with direct in-person patient contact who received their first two doses within 28 days or less can get a third dose six months after their second one. Moderately to severely immunocompromised islanders may be able to receive a third dose 28 days after their second one. Those who must travel for work or school and received mixed vaccine doses may also be eligible to get an additional matching mRNA vaccine dose.

Newfoundland and Labrador: Moderately to severely immunocompromised individuals may be eligible to receive an additional mRNA vaccine dose four weeks after the second one. Those who underwent a mixed vaccine course and need to travel for work or a medical procedure outside of Canada or attend school outside of the country are also eligible for a third dose.

Yukon: Booster shots are available to all residentsaged 50 and up, six months after their primary vaccine course. Currently, clinics are available in Whitehorse, Carmacks, Dawson City, Haines Junction and Mayo. However, the territory says clinics will be held in other communities “in the coming weeks.” Third doses are also available to those who may be immunocompromised, 28 days after their second vaccine dose.

Northwest Territories: All residents who are or will be 18 years of age by the end of 2021 are eligible for a booster shot six months after their second dose. People who are severely immunocompromised, as well as front-line health-care workers in Yellowknife and Behchoko, are eligible for an additional mRNA vaccine dose.

Nunavut: COVID-19 booster shots are available to all residents 12 and up who received their second dose of an approved vaccine more than six months ago.

With files from CTVNews Vancouver's Alyse Kotyk and Hannah Jackson