Some immunocompromised individuals may require an additional dose of a COVID-19 vaccine following a one-or-two-dose primary series, the Public Health Agency of Canada (PHAC) said Friday.
Based on new recommendations from the National Advisory Committee on Immunization (NACI), Canada’s Chief Public Health Officer, Dr. Theresa Tam, advised “an additional dose, or third dose of COVID-19 vaccine, for moderately or severely immunocompromised people who are more likely to have had a less than adequate immune response to the initial one or two dose COVID-19 vaccine series.”
“NACI continues to examine the need for booster doses, which unlike additional doses are intended to restore initially adequate immune protection that may have waned over time,” Dr. Tam said, speaking to reporters Friday.
The NACI advice also mentioned that people who are moderately to severely immunocompromised are shown to have a weaker response to vaccinations.
It recommended that those who are not yet vaccinated should receive three doses of an mRNA vaccine.
It said that an additional dose of an mRNA vaccine should be provided to those who are fully vaccinated, including those who received mixed vaccine shots.
Dr. Tam said the advice applies to people 12 and up 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. “Talk to your health provider and discuss your particular situation.”
The national advisory panel further stated that offering a third COVID-19 vaccine dose to those who are immunocompromised is different than giving a booster shot to the general population because for most, two doses of vaccine protects against the coronavirus.
“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.”
Even without the official advice, provinces like Ontario and Alberta have relied on their own health experts and gone ahead with offering third doses to those considered more medically vulnerable, such as seniors living in long-term care and patients who received transplants, are undergoing cancer treatments or are otherwise immunosuppressed.
Saskatchewan announced Friday that it too would begin giving a third shot to seniors starting in October. It said third doses would start being administered this week to those who are immunocompromised.
— With files from The Canadian Press