The National Advisory Committee on Immunization (NACI) has recommended that some immunocompromised individuals receive a third COVID-19 vaccine dose.
The new guidance was released by the Public Health Agency of Canada (PHAC) on Friday, and is based on NACI’s advice and scientific evidence.
It advises that some immunocompromised individuals should have an additional vaccine dose following a standard one or two dose primary vaccine series.
In Canada, a “primary vaccine series” is two doses of the Pfizer-BioNTech, Moderna, or AstraZeneca vaccines, or one dose of the Johnson & Johnson vaccine.
NACI noted that this additional dose is different from a booster shot, which restores immune protection that may have waned over time.
The additional dose, however, provides increased protection to those who had a “less than adequate” response to a primary vaccine series.
“The general population develops a robust immune response to COVID-19 vaccines,” NACI stated.
“Evidence to date shows that some immunocompromised individuals have a lower immune response to COVID-19 vaccines compared to the general population.”
Studies have shown, NACI said, that “moderately to severely immunocompromised” people who had either a reduced immune response, or none at all, after two doses of an mRNA vaccine can have an increased response after a third shot.
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The recommendation applies to several groups, including those who are undergoing treatment for a tumor, and organ transplant recipients.
“An additional dose contributes to health equity,” NACI said.
“[It provides] another opportunity for immunocompromised individuals to develop a better immune response which could offer better protection against COVID-19.
According to Chief Public Health Officer Dr. Theresa Tam,, 85% of eligible Canadians have received their first vaccine dose, and 78% are fully vaccinated.