Friday November 12, 2021 | NATIONAL
by Mary P Brooke, B.Sc., Editor | Island Social Trends
Two mRNA vaccines offered for protection against COVID-19 are now approved for use in Canada.
Today Health Canada announced that it has authorized Moderna’s COVID-19 vaccine (brand name Spikevax) for use as a booster shot. Earlier this week, Health Canada approved Pfizer-BioNTech’s vaccine (brand name Comirnaty) for use as a booster.
The Moderna booster shot will be half a dose, Health Canada said in a news release today. That makes it quite a different option compared to the Pfizer booster, which is a full dose. The differential adds to the complexity of decision-making for public health delivery and individuals regarding their own health choices.
Booster comes third:
“The booster shot is designed to help people maintain their protection against COVID-19 over time,” it was stated in the release. For a few weeks now the mention of ‘waning’ effectiveness of COVID vaccination has been mentioned by public health officials including Dr Theresa Tam nationally (she’s the Chief Public Health Officer of Canada) and Dr Bonnie Henry in BC (Provincial Health Officer).
The interval debate:
Both the Moderna and Pfizer booster shots are authorized for adults 18 years of age and older to be given at least six months after the regular second dose.
Evidence has grown during this year that increasing the interval between the first and second doses offers better protection. Dr Henry was on top of that early in the year — at one point heralding an 11-week interval as best (many seniors in the community thereby got their second dose this summer based on the 11-week target).
“A COVID-19 booster shot is an extra dose of the vaccine given after completion of the primary vaccine series,” the news release said. The mRNA primary vaccine series (for either Pfizer or Moderna) is two doses, administered at an interval is that is still a matter of debate and keeps changing.
As recently as this week (during her November 9, 2021 COVID update), Dr Henry said about the booster interval in BC, that “eight weeks is minimum, and four to five months is fine”. People who were offered their second dose at the end of this summer were offered a four-week interval (28 days); that was part of a rush to get people back onto post-secondary campuses, but seems like a cognisant failure of public health policy (even at the time, the recommended interval was 6 to 8 weeks, or 42 to 56 days).
Boosters for targeted populations:
In BC, the booster has already been rolling out to elderly and staff in long-term care, and people who are considered clinically vulnerable (i.e. mostly those who are immunocompromised), as well as health-care workers (as many of them were immunized early-on, starting December 2020, and mostly at that time with AstraZeneca which has shown less efficacy than the mRNA vaccines).
For everyone else, it will come, by invitation, “mostly five to six months” after a person’s second dose, Dr Henry said on November 9.
At the end of October, the National Advisory Committee on Immunization (NACI) recommended boosters for other high-risk groups, including people 70 years of age and older.
It also recommended boosters for front-line health-care workers who had a short period of time between their first two shots, as
NACI also recommended boosters for people who received two doses of the AstraZeneca vaccine, as the mRNA vaccines appear to offer better protection.
- Health Canada approves Pfizer’s COVID-19 vaccine for use as booster (November 9, 2021 – CBC)
- PHO: COVID can’t be ‘weathered’, get vaccinated (October 12, 2021 – Island Social Trends)
- Recommended COVID vaccine interval is longer than 28 days (September 18, 2021 – Island Social Trends)
- COVID in BC: Now 28-day interval for anyone needing 2nd dose (August 9, 2021 – Island Social Trends)