As more evidence emerges on the efficacy of the third dose of the COVID-19 vaccine, experts say it is high time public health officials revise the definition of “fully vaccinated” to include a booster dose.
While most SARS-CoV-2 vaccines available in Canada were initially developed and tested to contain two doses – with the exception of the Johnson & Johnson vaccine – a primary course should consist of three doses, Colin said. Furness, infectious disease specialist in epidemiology from the University of Toronto.
“Someone who’s only had two shots will say, ‘I’m fully vaccinated,’ and that’s what the officials are saying, [but] The officials got it wrong,” Furness told CTVNews.ca in a telephone interview on June 1. “When we look at the decrease in immunity after the second dose, it is, in fact, a three-dose vaccine.”
A newly released meta-analysis conducted by the Chinese University of Hong Kong earlier this year assessed the efficacy of different vaccine combinations in protecting against COVID-19. Including 53 studies involving more than 100 million people, the meta-analysis showed that three doses of an mRNA vaccine were highly effective in protecting against COVID-19 infection, whether symptomatic or asymptomatic, by 96 percent. Feather.
Three doses of the mRNA vaccine also had a 95 percent efficacy rate in reducing hospitalizations related to COVID-19. The study concludes that three doses of a COVID-19 vaccine are necessary to protect against infection with the Omicron version of the virus.
Despite this, the Public Health Agency of Canada’s (PHAC) definition of “fully immunized” with respect to COVID-19 vaccines refers to those who have received the primary series of vaccines. The primary series consists of two doses of most vaccines approved for use in Canada (such as the mRNA vaccine, 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 effectiveness of vaccines being used in Canada and may provide further recommendations on the definition of a fully vaccinated individual.” ,” PHAC spokeswoman Anna Madison wrote in an email to CTVNews.ca on June 1.
It’s important to note that as the COVID-19 pandemic has progressed, the SARS-CoV-2 virus has evolved away from the vaccine it was initially developed to target, Furness said. This viral development has reduced the efficacy of current vaccines, especially when it comes to protection against infection with Omicron, the latest version of the concern. Despite this, the three doses of the vaccine continue to provide solid protection, particularly against serious consequences of COVID-19 such as hospitalization and death, Furness said. As a result, he said he expected to see a change in the definition of “fully vaccinated.”
“Imaginatively, if we had a vaccine that prevents long-term COVID, hospitalization, and death, but doesn’t prevent anyone from becoming infected, I would call it a wildly successful; We’ll all get a cold… but no one will get really sick,” Furness said. “There’s no question we don’t have that, but three doses of a COVID-19 vaccine would have gotten us closer to that.” Is.
“When we talk about ‘fully vaccinated,’ we should be talking about three [doses],
In Canada, only 20 million third and fourth doses of the COVID-19 vaccine have been given so far, based on data compiled by CTVNews.ca. According to PHAC, about 55.5 percent of Canadians aged 12 and older are vaccinated with three doses of the COVID-19 vaccine, which translates to about 18.5 million people.
‘Fully immunization’ is no longer enough
Dr. Nazeem Muhajrin, an epidemiologist at the University of Saskatchewan, also advises people who are eligible for and receive their third dose of the COVID-19 vaccine. However, instead of tying the definition of “fully immunized” to a specific number of doses, he called for public health officials to keep their vaccination status “up-to-date” to Canadians based on the latest recommendations from the national advisory. The focus should be on giving advice. Immunization Committee (NACI).
“‘Fully vaccinated’ no longer works, in my mind, as a definition of being up-to-date on the dose of vaccine you need to receive … I think it’s high time that we [change] That,” he told CTVNews.ca in a telephone interview on June 1. “It’s all about getting caught up with the vaccines that you are recommended to get at this stage of the pandemic.”
The World Health Organization’s current 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 people fully immunized with at least one dose of Johnson & Johnson vaccine or two doses of any remaining vaccines approved for use in Canada. However, provincial governments such as Ontario have updated the wording in their latest guidance to suggest that people receive “all recommended COVID-19 vaccine doses, including any booster doses, when eligible.”
Additionally, provinces across Canada have now made a third dose available for people 12 years of age and older, and the NACI strongly recommends a third dose for all adults in Canada.
While Furness said he believes the COVID-19 vaccine protection may also decrease after the third dose, he still recommends that people who are eligible to receive their booster shots do so, it is only two Provides additional protection compared to over dosage.
“It may be less, but it will still really disrupt transmission and it will interrupt outbreaks, if we can get enough people.” [vaccinated] With the third dose,” he said.
Muhajrein said a third dose of the COVID-19 vaccine would also help protect the population from new variants or sub-variants that may emerge in the future.
“As long as we have many types spreading, that opens up the possibility for new forms to emerge – that’s how these forms evolve,” he said. “I really don’t see any evidence-based reason for keeping ‘fully immunized’ only for the two primary doses.”
Both Furness and Muhajrin said that the uptake of the third dose of the COVID-19 vaccine has been slow compared to the first and second doses. One reason for this is that the vaccine was initially offered to the public as two doses, which made people feel they needed to be adequately protected, Furness said.
“That’s the mental model most people had,” he said. “So when we started saying you need a third dose now… [they] Said, ‘You sold us an idea that there was a two-dose vaccine and I signed on, now you’re turning the deal and I don’t like it, I’m walking away.'”
Muhajrin said earlier this year contributed to a lack of enthusiasm by provincial governments across the country to increase vaccine mandates. For example, those who are unable to enter restaurants or movie theaters, for example, no longer need proof of vaccination.
“The vaccine mandate really works in terms of getting people who are eligible to get a second dose,” Muhajrin said. “But when governments start rolling back those public health measures and vaccine mandate measures, I think people have really lost that incentive.”
Encouraging Canada to Promote
While he calls on public health officials to include a third dose in the definition of “fully vaccinated,” Furness said it would take more than just changing the definition to encourage people to actually get their booster shot. . Part of the solution lies in vaccine mandates being implemented and implemented by employers and governments.
,[If] Your employer has made vaccination mandatory and that changes to three doses, then we’re going to have a really important public conversation about what the risks and benefits are,” Furness said. “Once we have enough critical public There will be talks, then people will start thinking about it… [otherwise] It would just seem like a bureaucratic ploy.”
Furness said an open dialogue about the role of vaccines in the fight against COVID-19 would be helpful especially targeting those who are suspicious or fear vaccination. Furness said part of the solution is to increase education on how vaccines work, as well as better public health messaging and more local engagement.
“It’s scary, suspicious, somewhat suspicious” [group] Not sure what to believe, and anyone in that category is going to default to nothing unless you make a good case – that’s where work has to be done, said Furness.
Muhajrin said that based on his comments, the appetite for vaccine mandates across Canada is low at the moment. But one scenario in which he could see these rules being reimposed at the provincial level is if governments see another wave of cases, or if another variant or sub-version emerges, he said. In that case, it is important that officials do not wait too long to act, Muhajrein said.
“Provincial governments have the authority and responsibility to implement policies that keep their populations safe,” he said. “During Covid-19, what we have learned is that quick action is what really matters. We can’t wait until COVID really starts hurting us to take action against it. ,
Furness also said that as drug companies move closer to developing an Omicron-specific vaccine, it is likely to encourage more people to take their third dose if they haven’t already.
“If we can come back and say, ‘Look, the vaccine is back that a lot of people want to understand,’ that’s a reduction in my risk of getting infected … I think it’s more in the sails. Will put air in,” said Furness. “And that will make it easier to maintain the vaccine mandate.”
While Furness said a case could be made for waiting until a type-specific vaccine is developed before considering revising the definition of immunization as a whole, he and other experts recommend that those who are eligible should be treated later. Get vaccinated as soon as possible.
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