As more evidence emerges about the effectiveness of third doses of COVID-19, experts say it is high time that public health authorities reconsider the definition of “fully vaccinated” to include a booster dose.
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 primary course should consist of three doses, said Colin Furness, an infectious disease expert. diseases epidemiology from the University of Toronto.
Someone who has only had two vaccines will say, “I’m fully vaccinated,” and that’s what the authorities say. [but] the authorities were mistaken, “Furnes told CTVNews.ca in a telephone interview on June 1. “When we look at the decline in immunity after the second dose, it’s really a three-dose vaccine.”
A recently published meta-analysis conducted by the Chinese University of Hong Kong earlier this year evaluated the effectiveness of various combinations of vaccines to protect against COVID-19. Including 53 studies involving more than 100 million people, the meta-analysis showed that three doses of mRNA vaccine were highly effective in protecting against COVID-19 infection, whether symptomatic or asymptomatic, in 96 percent.
Three doses of mRNA vaccine also had a 95 percent efficacy in reducing COVID-19-related hospitalizations. The study concluded that three doses of the COVID-19 vaccine were needed to prevent infection with the Omicron virus variant.
However, the Canadian Public Health Agency’s (PHAC) definition of “fully vaccinated” for COVID-19 vaccines continues to apply to those who have received a primary batch of the vaccine. The primary series includes two doses of most vaccines approved for use in Canada (such as mRNA vaccines, as well as AstraZeneca, Novavax and Medicago vaccines) or one dose of Johnson & Johnson vaccine.
“As the epidemiological context of COVID-19 continues to evolve, the Government of Canada will continue to monitor the efficacy and effectiveness of vaccines used in Canada and may make further recommendations on the definition of a fully vaccinated person,” a PHAC spokesman said. Anna Madison wrote in an email to CTVNews.ca on June 1.
It is important to note that as the COVID-19 pandemic progresses, the SARS-CoV-2 virus has evolved beyond what vaccines were originally designed for, Furnes said. This viral evolution has reduced the efficacy of current vaccines, especially when it comes to protecting against Omicron infection, the latest option of concern. However, three doses of the vaccine continue to offer solid protection, especially against severe COVID-19 outcomes such as hospitalization and death, Furnes said. As a result, he said he hoped to see a change in the definition of “fully vaccinated”.
“Hypothetically, if we had a vaccine that prevented prolonged COVID, hospitalization and death, but did not prevent anyone from getting infected, I would call it extremely successful; we would all get a cold … but no one would really get sick, “Furness said.” There’s no doubt we don’t have that, but three doses of COVID-19 vaccine brings us closer.
“When we talk about ‘fully vaccinated’, we have to talk about three [doses]”
In Canada, just over 20 million third and fourth doses of the COVID-19 vaccine have been administered to date, based on data collected by CTVNews.ca. According to the PHAC, about 55.5% of Canadians aged 12 and over have been vaccinated with three doses of COVID-19, which means approximately 18.5 million people.
“FULLY VACCINATED” IS NO LONGER ENOUGH
An epidemiologist at the University of Saskatchewan, Dr. Nazim Muhajarin, also advises those eligible for their third dose of the COVID-19 vaccine to go and get it. However, instead of linking the definition of “fully vaccinated” to a number of doses, he said public health authorities should focus on advising Canadians to keep their vaccination status “up-to-date” based on recent recommendations from the National Advisory Committee. Immunization (NACI).
“Fully vaccinated” no longer works in my opinion as a definition of keeping up with the doses of vaccines you need to get… I think it’s high time [change] this, “he told CTVNews.ca on June 1 in a telephone interview.
The current World Health Organization definition of a primary vaccination series refers to one or two doses of COVID-19 vaccine approved for emergency use, depending on the product. In the context of international travel, the Government of Canada considers that those with at least one dose of Johnson & Johnson vaccine or two doses of any of the other vaccines approved for use in Canada have been fully vaccinated. However, provincial governments such as Ontario have updated the wording in their latest guidelines to suggest that people be vaccinated with “all recommended doses of COVID-19 vaccine, including each booster dose (s) when eligible.”
In addition, provinces in Canada have already provided third doses for those aged 12 and over, and NACI strongly recommends third doses for all adults in Canada.
Although Furnes said he acknowledged that protection against the COVID-19 vaccine may also weaken after the third dose, he nevertheless advised those eligible to have a booster to do so, given the added protection. which offers compared to only two doses.
“It may lose weight, but it would still interrupt the broadcast and break out the outbreaks if we manage to get enough people. [vaccinated] with a third dose, “he said.
A third dose of the COVID-19 vaccine will also help further protect populations from new variants or sub-variants that may emerge in the future, Muhajarin said.
“While we have many common variants, this opens up the possibility of new variants – that’s how the evolution of these variants happens,” he said. “In fact, I don’t see an evidence-based reason to keep ‘fully vaccinated’ up to two primary doses.”
The absorption of the third dose of the COVID-19 vaccine is slow compared to the first and second doses, Furnes and Muhajarin said. Part of the reason for this is that the vaccine was originally presented to the public in two doses, which makes people think it’s all they need to be protected enough, Furness said.
“This is the mental model that most people had,” he said. “So when we started saying you needed a third dose now?” [they] said, “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.”
Contributing to this lack of enthusiasm for boosting was the lifting of vaccine mandates by provincial governments across the country earlier this year, Muhajarin said. Those who cannot enter restaurants or cinemas because, for example, they have not been vaccinated are no longer banned and proof of vaccination is no longer required.
“Vaccine obligations work to actually attract people who qualify for a second dose,” Muhajarin said. “But when governments began to withdraw these public health measures and vaccine mandate measures, I think people really lost that incentive.”
ENCOURAGING CANADIANS TO BE SUPPORTING
Although he called on public health authorities to include third doses in the definition of “fully vaccinated”, Furnes said it would take more than changing the definition to encourage people to actually get a booster vaccine. Part of the decision lies in vaccine mandates, which are implemented and enforced by employers and governments.
“[If] your employer has ordered a vaccination and this is changed to three doses, then we will actually have a significant public discussion about the risks and benefits, ”Furness said. “Once we have a significant enough public conversation, people will start thinking about it.” [otherwise] it will seem like a bureaucratic move. “
An open conversation about the role of vaccines in the fight against COVID-19 will be especially helpful in targeting those who doubt or fear vaccination, Furnes said. Part of the solution lies in increased education on the function of vaccines, as well as improved public health communications and more local engagement, Furnes said.
“It’s so scary, so suspicious, a little skeptical [group] “It’s not certain who to trust, and everyone in that category will by default do nothing until you present a good case – that’s where it should end,” Furness said.
Based on his observations, appetite for vaccine mandates in Canada remains low at the moment, Muhajarin said. But one scenario in which he can see these rules being reintroduced at the provincial level is if governments see a new wave of cases or if another option or sub-option emerges, he said. In this situation, it is extremely important that employees do not wait too long to act, Muhajarin said.
“Provincial governments have the power and responsibility to put in place policies to keep their people safe,” he said. “During COVID-19, what we learned was that rapid action really does matter. We can’t wait for COVID to really hurt us to act against it. “
Furness also said that as pharmaceutical companies approach the development of an Omicron-specific vaccine, they are likely to encourage more people to receive their third dose if they have not already done so.
“If we can go back and say, ‘Look, the vaccine …
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