Populations at highest risk of waning protection following their primary series and at highest risk of severe COVID-19 illness should be offered a booster dose of an mRNA COVID-19 vaccine at least six months after completing their primary series,NACI’s new guidance released Friday said, (new window) noting that seniors 80 years and older
shouldbe offered a booster shot.
NACI also said other people
maybe offered a booster shot, because they
may be at increased risk of lower protection over time since vaccination, increased risk of severe illness or who are essential for maintaining health system capacity.
Those groups include:
- Adults between the ages of 70 and 79.
- People who received two doses of the AstraZeneca/COVISHIELD vaccine or one dose of the Janssen vaccine.
- Adults in or from First Nations, Inuit and Métis communities.
- Adults who are front-line health-care workers who have direct in-person contact with patients and who were vaccinated with a very short interval between their first and second doses (three or four weeks).
Booster shots should be given at least six months after the second dose of vaccine, NACI said. The boosters should also be one of the mRNA vaccines — Pfizer-BioNTech or Moderna, it said.
NACI has already recommended third doses for people living in long-term care home sor other congregate settings, as well as people with specific immunocompromising conditions
In its guidance on Friday, the advisory group said it continues to
strongly recommend that people who are moderately to severely immunocompromised should get a third dose of vaccine. People in that category include:
- Active treatment for solid tumour or blood cancers.
- Organ transplant recipients taking immunosuppressive therapy.
- People getting chimeric antigen receptor (CAR)-T-cell therapy or hematopoietic stem cell transplant (within two years of transplantation or taking immunosuppression therapy).
- Moderate to severe primary immunodeficiency (e.g. DiGeorge syndrome, Wiskott-Aldrich syndrome).
- Stage 3 or advanced untreated HIV infection and those with AIDS.
- Active treatment with certain immunosuppressive therapies.
What’s the difference between a booster shot and a 3rd dose?
The three approved COVID-19 vaccines in Canada (Pfizer-BioNTech, Moderna and AstraZeneca) are all two-dose regimens. A third dose is for people who may not have mounted a strong enough immune response to fight off COVID-19 after two doses.
NACI has identified two populations that require third doses: elderly people living in long-term care and those who have specific health conditions that make them immunocompromised (including organ transplant recipients). For these people, a third dose is an extension of their primary series of vaccinations.
A booster shot is for people who likely had a fulsome immune response to the regular two-dose vaccine regimen, but
with time, the immunity and clinical protection has fallen below a rate deemed sufficient in that population, according to the World Health Organization (WHO) .
It’s comparable to the tetanus vaccine, which requires a booster shot every 10 years. Most experts agree that everyone will likely need a COVID-19 booster shot at some point within the next year, but the big question is when.
Nicole Ireland · CBC News