Canada’s National Advisory Committee on Immunization recommends seniors and other high-risk groups be offered a booster dose of COVID-19 vaccine, according to new interim guidance.
The guidance, released Friday morning, says that adults aged 80 and older should be offered a booster dose of COVID-19 vaccine, at least six months after receiving their second shot. Seniors living in long-term care should also be offered a booster dose, NACI noted, in line with the group’s previous recommendation.
A number of other populations “may” be offered a booster shot, the guidance reads. These include seniors aged 70 to 79, people who received two doses of the AstraZeneca vaccine or one dose of the Janssen vaccine, adults in or from First Nations, Métis and Inuit communities, and frontline health-care workers who have direct contact with patients and who received their initial vaccines with a short interval between doses.
More than 220,000 Canadians received two doses of AstraZeneca’s vaccine, according to data from the Public Health Agency of Canada.
A handful of provinces and territories have already announced that they will offer booster shots to certain populations, including British Columbia, Yukon and Northwest Territories.
On Friday morning, Ontario’s Health Minister Christine Elliott said on Twitter that the provincial government would release information next week on when Ontarians can expect their booster dose.
Either mRNA vaccine, Moderna or Pfizer-BioNTech, can be offered as a booster dose, NACI says.
The organization said it made its decision based on evidence showing that immunity provided by the vaccine could wane over time.
“Evidence suggests protection against infection decreases as time since completion of the primary vaccine series increases,” the guidance says.
“Studies suggest that a booster dose of an mRNA COVID-19 vaccine produces a very good immune response that is generally higher than the immune response after the primary series, has a favourable safety profile, and provides good short-term protection against infection.”
Dr. Theresa Tam, chief public health officer of Canada, said the evidence shows that some people might need a third shot to increase their protection against COVID-19.
“While COVID-19 vaccines in use in Canada continue to be very effective in protecting most people against serious illness due to COVID-19, emerging evidence suggests vaccine effectiveness against infection may decrease over time in some situations,” she said at a press conference Friday.
Recommendations for First Nations and other Indigenous communities were made taking into consideration some other factors — like overcrowded living conditions — that might make people there more vulnerable to COVID-19, Tam said.
With regard to boosters for people who received the AstraZeneca or Janssen vaccine, she said, these vaccines had lower effectiveness to begin with, “and these vaccine recipients may be susceptible to infection sooner.”
Some health-care workers also got their two doses with a very short interval of less than 28 days in between, she said, and evidence so far indicates that a longer interval provides better protection.
However, she noted that so far, the committee has not found evidence that the general population should get a booster shot.
“There is no evidence of any widespread waning of protection against severe disease in the general population that has been vaccinated against COVID-19,” she said. “So boosters for the general population are not required at this time.”
She emphasized the importance of getting more Canadians their first and second doses, rather than focusing on boosters.
“Getting more people to complete their two-dose primary series remains a key focus of the immunization efforts in Canada,” she said.
Between now and early 2022, evidence on vaccine boosters might change and NACI might issue further recommendations on booster shots for the broader population, said Dr. Howard Njoo, deputy chief public health officer of Canada.
—with files from The Canadian Press