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As we approach the end of the year, health experts and officials in Canada are facing questions about booster shots for COVID-19, including when the general population will need them.
On Oct. 29, the National Advisory Committee on Immunization (NACI) released interim guidance on the use of booster shots in Canada, which states that Canadian populations "at highest risk of waning protection" and "at highest risk of severe COVID-19 illness" should be offered a booster shot of an mRNA COVID-19 vaccine at least six months after completion of their primary vaccination series.
These populations are specifically adults living in long-term care or other congregate care settings for seniors, and all adults age 80 and older.
NACI also stated that boosters may be offered a at least six months after the primary course of vaccination if individuals fall into the following categories:
Adults 70 to 79 years of age
People who received two doses of the AstraZeneca Vaxzevria/COVISHIELD vaccine or one dose of the Janssen vaccine
Adults in or from First Nations, Inuit and Métis communities
Adults who are frontline healthcare workers who have direct in-person contact with patients and who were vaccinated with a very short interval
"There is currently no evidence of widespread waning of protection against severe disease in the general Canadian population who have been vaccinated against COVID-19," the NACI guidance reads.
"Emerging evidence suggests vaccine effectiveness against asymptomatic infection and mild COVID-19 disease may decrease over time. A booster dose could help restore and maintain protection against infection in certain populations. It is currently unknown how long effectiveness from a booster dose may last."
The priority in Canada still remains administering as many first and second doses of a COVID-19 vaccine as possible.
"With over 5.5 million adults and eligible youth yet to be fully vaccinated in Canada, it is important to emphasize that getting more people to complete their two-dose primary series remains a key focus of the COVID-19 immunization effort in Canada," a statement from Dr. Theresa Tam, Canada's chief public health officer, reads.
In an interview with CTV News, Dr. Tam said that while the Canadian data shows that we still have "great protection against severe outcomes" from COVID-19 in the country, the general population may need a booster dose next year, but "not right now."
A study conducted by Israel’s Clalit Research Institute and researchers from Harvard University found that administering a third dose of Pfizer/BioNTech vaccine reduced COVID-19-related hospitalization by 93 per cent, reduced severe COVID-19 disease by 92 per cent and COVID-19-related deaths by 81 per cent, compared to individuals who received two doses.
This study examined data on 728,321 individuals in Israel who received a third dose of the Pfizer/BioNTech vaccine, compared with 728,321 individuals who received two doses at least five months prior.
"These results show convincingly that the third dose of the vaccine is highly effective against severe COVID-19-related outcomes in different age groups and population subgroups, one week after the third dose. These data should facilitate informed policy decision-making," a statement from Ran Balicer, senior author of the study, director and chief innovation officer of the Clalit Research Institute, reads.