A national advisory panel recommended Friday people who are immunocompromised should receive a third vaccine dose against COVID-19.
It's the latest piece of advice to come from the National Advisory Committee on Immunization (NACI), which says people who are moderately to severely immunocompromised are shown to have a weaker response to vaccinations.
These individuals also stand a greater risk of developing complications and dealing with the infection for longer if they contract COVID-19, according to the committee.
"An additional dose contributes to health equity by providing another opportunity for immunocompromised individuals to develop a better immune response which could offer better protection against COVID-19," NACI says in written advice.
It recommends those who are not yet vaccinated to receive three doses of an approved mRNA vaccine, which in Canada means shots from either Moderna or Pfizer-BioNtech
The committee also calls for giving an additional dose of one of these shots to immunocompromised people who have been double vaccinated, including those who received mixed doses.
"This is not unusual for immunocompromised groups, where we often recommend different vaccine schedules to help them achieve better protection," Dr. Shelley Deeks, committee chair, said in a statement.
"This is different from a booster dose, which would be used to boost an immune response that has waned over time."
The committee says people should consider taking a viral-vector vaccine like AstraZeneca only if they have a medical reason that makes them unable to take one of the mRNA vaccines, or can't access one.
Canada's chief public health officer Dr. Theresa Tam says the advice applies to people 12 and older whose immune systems are compromised for a variety of reasons like being treated for a tumour or having an untreated HIV infection that has advanced.
"There's a very broad group of individuals who may have either underlying health condition or a treatment that's rendered them more immunocompromised," she said at a briefing Friday.
"Talk to your health provider and discuss your particular situation."
The advisory body says giving those who are immunocompromised a third dose is different than offering a booster shot to the general population because for most two doses of vaccine protect against COVID-19.
The panel says it continues to study the need for booster shots for specific groups, like those in long-term care.