As more evidence emerges of the effectiveness of third doses of the COVID-19 vaccine, experts say it is time for public health authorities to revise the definition of a “complete vaccine” to include a reminder dose.
Cullen said that while most SARS-CoV-2 vaccines available in Canada were originally developed and tested to include two doses — with the exception of the Johnson & Johnson vaccine — the initial course should consist of three doses rather than three. Epidemiology from the University of Toronto.
“A person who only had two vaccinations would say, ‘I’ve only had two vaccinations,'” and that’s what the authorities say, [but] “The authorities got it wrong,” Furness told CTVNews.ca in a June 1 phone interview. When we look at the deterioration of immunity after the second dose, it’s really three shots.
A newly published meta-analysis conducted by the Chinese University of Hong Kong earlier this year evaluated the effectiveness of different vaccine combinations in protecting against COVID-19. Participating in 53 studies involving more than 100 million people, a meta-analysis showed that three doses of the mRNA vaccine were highly effective in protecting against COVID-19 infection, both asymptomatic and asymptomatic, by 96%.
Three doses of the mRNA vaccine also had a 95% efficacy rate in reducing hospitalizations associated with COVID-19. The study concluded that three doses of the COVID-19 vaccine are needed to protect against infection with the Omicron variant of the virus.
Despite this, Public Health Canada’s (PHAC) definition of “full vaccination” for COVID-19 vaccines continues to refer to people who have received an initial series of vaccinations. The initial series includes two doses of most vaccines approved for use in Canada (such as the mRNA vaccines, as well as the AstraZeneca, Novavax, and Medicago vaccines) or a single dose of the Johnson & Johnson vaccine.
“As the epidemiological context of COVID-19 continues to evolve, the Government of Canada will continue to monitor the efficacy and efficacy of vaccines used in Canada and may make additional recommendations about the definition of a complete vaccine,” said Anna Madison, a spokeswoman for the Primary Health Care Center. He wrote in an email to CTVNews.ca on June 1.
Importantly, as the COVID-19 pandemic progressed, the SARS-CoV-2 virus moved away from vaccines that were originally developed to target it, Furness said. This viral evolution has reduced the efficacy of current vaccines, especially with regard to protection against infection by Omicron, a worrisome new alternative. Despite this, three doses of the vaccine still provide strong protection, particularly against severe consequences of COVID-19 such as hospitalization and death, Furness said. As a result, he said he hoped to see a change in the definition of “fully pollinated.”
“Hypothetically, if we had a vaccine that prevented COVID for a long time, hospitalization and death, but didn’t prevent anyone from getting infected, I would call it a wow; we’d all catch a cold…but no one would really get sick,” Furness said. There’s a doubt we don’t have that, but three doses of the COVID-19 vaccine bring us closer to that.
When we say ‘fully immunized’, we should be talking about three [doses]. “
In Canada, just over 20 million third and fourth doses of the COVID-19 vaccine have been administered so far, according to data compiled by CTVNews.ca. According to the PHAC, approximately 55.5% of Canadians age 12 or older receive three doses of the COVID-19 vaccine, which represents about 18.5 million people.
‘Fully fortified’ is no longer enough
University of Saskatchewan epidemiologist Dr. Nazim Mohajer also advises those who qualify for the third dose of the COVID-19 vaccine to receive it. However, rather than linking the definition of “full vaccination” to a specific number of doses, he said public health authorities should act to advise Canadians to keep their vaccination status “up-to-date” based on the latest National Immunization Advisory Committee (NACI) recommendations.
“‘Full vaccination’ no longer works, in my opinion, as a definition to keep up with the latest doses of vaccines you need… I think it’s time [change] This,” he told CTVNews.ca on June 1 in a phone interview. “It’s about getting to know all the vaccines that are recommended at this point in the pandemic. »
The current WHO definition of a primary vaccination series refers to one or two doses of COVID-19 vaccines approved for emergency use, depending on the product. In the context of international travel, the Government of Canada considers individuals who have had at least one dose of Johnson & Johnson vaccine, or two doses of any of the remaining vaccines approved for use in Canada, to have been fully immunized. However, provincial governments such as Ontario have updated the wording of their latest guidelines to suggest that people be vaccinated “with all recommended doses of the COVID-19 vaccine, including any booster doses when they are eligible.”
In addition, provinces in Canada now make third doses available for people 12 years of age or older, and the NACI strongly recommends third doses for all adults in Canada.
While Furness said he accepts protection from a COVID-19 vaccine that may also wane after a third dose, he still recommends those who qualify for the booster, given the additional protection it provides, compared to just two doses.
“It might go down, but it will still really hinder transmission and it will cut epidemics, if we can get enough people [vaccinated] with a third dose.
Muhagen said a third dose of the COVID-19 vaccine will also help protect the population from new variants or sub-variables that may emerge in the future.
“As long as many variables are spread out,” he said, “it opens up the possibility of new variables emerging – that’s how the evolution of those variables happens.” “I really don’t see any evidence-based reason to maintain a ‘full vaccination’ with only two basic doses. »
Furness and Muhagen said absorption of the third dose of the COVID-19 vaccine was slow compared to the first and second doses. Part of the reason, Furness said, is that the vaccine was initially offered to the public as a two-dose, leading people to believe that was all they needed to protect appropriately.
“That’s the mental model that most people have,” he said. “So when we started saying you need a third dose now… [they] “You sold us the idea that there was a two-dose vaccine and I signed, now you’re changing the deal and I don’t like it, I’m leaving,” he said.
Muhagen said the lifting of vaccination mandates by regional governments across the country earlier this year contributed to this lack of enthusiasm that needs to be bolstered. Those who cannot enter restaurants or cinemas because they have not been vaccinated, for example, are no longer prohibited, and proof of vaccination is no longer required.
“The vaccination laws have worked in terms of making people eligible for a second dose,” Muhajir said. But when governments started eliminating public health measures and vaccine authorization procedures, I think people really lost that incentive. »
Encouraging Canadians to strengthen themselves
Although he called on public health authorities to include third doses in the definition of a “complete vaccine,” Furness said it would take more than changing the definition to encourage people to get the vaccine. Part of the solution lies in the implementation and enforcement of vaccination mandates by employers and governments.
” [If] Furness said the employer has made vaccination mandatory and will be up to three doses, so we’ll have an important public conversation about the risks and benefits. “Once we have enough important public conversations, people will start thinking about it… [otherwise] It would seem a simple bureaucratic decision.
Furness said that having an open conversation about the role vaccines play in fighting COVID-19 would be particularly useful in targeting those who doubt or fear getting vaccinated. Part of the solution also lies in increased education about the function of vaccines as well as better public health messaging and more local participation, Furness said.
“It’s just fear, doubt, somewhat skeptical [group] “Who doesn’t know who to believe, and anyone in that category will do nothing until you do well – that’s where it needs to be done,” Furness said.
Based on his observations, the desire to vaccinate across Canada remains low at this time, Mohagen said. But one scenario in which he could see reintroduction of these rules at the county level is whether governments see another wave of cases, or if another variable or sub-variable emerges. In this case, Mohagen said, it is essential that officials not wait too long to act.
“Regional governments have the authority and responsibility to implement policies that keep their people safe,” he said. “During COVID-19, what we’ve learned is that quick action really matters. We can’t wait for COVID to start really hurting us to take action against it.
Furness also said that as drug companies move closer to developing a vaccine for Omicron, it will likely encourage more people to get their third dose if they haven’t already.
“If we could go back and say, ‘Look, the vaccine is going to go back to what a lot of people want to understand,’ that’s reducing the risk of infection…I think that would put more winds in it. And that would make it easier to maintain the vaccination mandates,” Furness said. »
While Furness said it might be justified to wait for the development of a specific, variant vaccine before considering a full revision of the definition of vaccination, he and other experts recommend that those who are qualified do so as soon as possible.
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