Fourth doses of COVID-19 vaccines are being released to more Canadians eligibility opens across the countrybut research shows there are limits to the impact they can have on the highly contagious BA.5 Omicron subvariant fueling Canada’s first summer surge. Post increasing pressure from health workers and public To access additional shots, some provincial governments have expanded eligibility from just immunocompromised and elderly Canadians to anyone over 18. But the move is at odds with the National Advisory Committee on Immunization (NACI). recent recommendations that a second reminder should be given now only to those at highest risk of severe COVID-19, while younger Canadians could wait until the fall. The data show that while a third installment offers a significant increase in protection against infection, hospitalization and death — a fourth dose offers only marginal benefit against severe COVID-19 for most, including short-lived protection against infection, even in vulnerable groups. “That fourth dose adds a small, modest reduction in the risk of severe disease,” said Angela Rasmussen, a virologist at the Vaccine and Infectious Diseases Organization (VIDO) at the University of Saskatchewan. “But I think it’s also limited in what we can expect from it — I don’t think we can definitely expect this wave to stop.” BA.5 sparked an unexpected seventh wave across much of Canada, representing almost 40 percent of the time and leads to a significant increase in COVID-19 hospitalizationsdue to protection avoidance ability both from vaccination and previous infection. WATCHES | When is the best time to get a 4th vaccine for COVID-19?
When should you get the 4th vaccine for COVID-19?
Infectious disease expert Dr. Zane Chagla explains who should receive a second booster of the COVID-19 vaccine and when.
4th dose protection from infection short lived
A recent study from Israel published in New England Journal of Medicine (NEJM) found that while protection against infection and severe COVID-19 increased after a fourth dose in people over 60, the vaccine’s effectiveness began to wane after just a few weeks. A second study from Israel published in British Medical Journal (BMJ) found that while people aged 60 and over gained additional protection against hospitalization and death in the three weeks after the fourth vaccination, protection against infection “diminished rapidly”. Health workers were specifically examined in another Israeli study It was published in the NEJM and found that a fourth dose provided only a marginal difference in infection rates compared to those with a third shot and only a small difference in the severity of breakthrough symptoms. A new Canadian study published in BMJ analyzed the effectiveness of a fourth dose in long-term care residents in Ontario. It found that the jab initially improved protection against infection and severe COVID-19, but the duration of this protection “remains unknown.” “The science around this right now has only clearly demonstrated the benefits of this fourth dose of the vaccine for the groups that (NACI) has described,” said Dr. Fahad Razak, an internist at St. Michael’s in Toronto and scientific director of Ontario’s COVID-19 Scientific Advisory Panel, said The current on July 7. “Who are older people and people who are immunocompromised or at high risk.” A patient receives a dose of the Pfizer COVID-19 vaccine in London in 2021. (Alberto Pezzali/The Associated Press) The research shows that while there are some people who benefit from the fourth dose, including long-term care residents, the elderly and other vulnerable groups, there is a lack of data showing a clear benefit for people under 60. Dr. Zain Chagla, an infectious disease physician at St. Joseph’s Healthcare Hamilton and associate professor at McMaster University, said older, immunocompromised Canadians may benefit from a fourth dose — but younger groups have “very little benefit.” “I don’t think there’s going to be a huge benefit here. It’s certainly not going to change the dynamics of the pandemic in terms of less disease. Really, to have any effect of taking the edge off, you’d need almost everyone to be taking fourth doses almost immediately,” he said. “And even then, look, their immunity will wane in six to eight weeks and you’ll see they won’t really be protected from infection anyway and BA.4 and BA.5 will still be here in six to eight weeks ».
The 3rd dose intake is still missing in Canada
While the extension of the fourth tranche to more Canadians could now have a limited impact on the trajectory of the BA.5-based wave across much of the country, the bigger problem lies in the abysmal uptake of third tranches across the country. Less than half of Canadians have received a third dose, which the research suggests adds significant protection against severe COVID-19, a number that has stagnated for months amid a growing push to extend the fourth dose. “The biggest issue right now is the significant number of Canadians who have not received a third dose,” said Dr. David Naylor, who led the federal investigation into Canada’s national response to the 2003 SARS outbreak and now co-chairs the federal COVID government. -19 special immunity group. “It’s increasingly clear that the bets for this vaccine are three shots, and we need to stop referring to people with two doses as fully vaccinated.” WATCHES | Why the 3rd and 4th COVID-19 shots are both important right now:
3rd and 4th shots of COVID-19 are both important right now, says expert
Infectious disease expert Dr. Isaac Bogoch explains who benefits most from a fourth dose of COVID-19, but also highlights the need for many people to simply get a third shot. But Naylor hopes that extending the fourth dose to more Canadians could have an impact on the spread of BA.5 across the country, even if the data does not yet show a clear benefit for younger age groups. “For someone younger and healthy who has had three shots and has a recent infection, I can see the logic of waiting to get a fourth shot,” he said. “There is no doubt that the marginal returns of a fourth dose are small at an individual level for this segment of the population — but they are at risk of re-infection, and wider coverage can help slow the spread at the population level.” Chagla said extending the fourth dose to younger Canadians now contrary to NACI guidelines could actually do more harm than good by encouraging more people to come back for a third dose. “There are going to be people who say, ‘Well, I’m getting dose two, they’re already saying I need a fourth dose, what’s the point of these vaccines if they didn’t protect me from getting Omicron?’” “Every one of those doses that goes out, the public image of what vaccines can do changes with them, and we need a lot of people to come back for their third dose.” Rasmussen of the University of Saskatchewan said her concern is that many Canadians may view the boosters as “optional” with limited immune benefit. He said messaging around third doses needs to be “home-packaged” to increase uptake. “This third dose provides a significant boost in protection against both serious disease and infection with Omicron BA.1,” he said. “This fourth dose is maybe incremental, maybe just a modest benefit, but the third dose I think is very clear. At least with BA.1, it provides significant benefits.”
Updated vaccines on the horizon
Timing boosters to ensure strong immune protection against COVID-19 are becoming increasingly critical with the emergence of Omicron’s highly contagious BA.4 and BA.5 subvariants, as well as a new subvariant leading a wave in India called BA.2.75. While Canadians who choose to receive a fourth dose of the original vaccine strain now may only be protected for several weeks against infection, updated bivalent vaccines that combine the original vaccine with protection from Omicron are also on the horizon. Modern bivalent vaccine it is one that many are pinning their hopes on. But experts worry that targeting the original Omicron strain may not be sufficient because research showing a lack of cross-protection against the very different variants BA.2.12.1, BA.4 and BA.5. “The usual argument for waiting is that we might get better vaccines in the fall. However, the data on bivalent vaccines is less compelling or complete than many of us had hoped,” Naylor said. Bivalent vaccines target the spike protein of the virus. They differ from newer, innovative platforms with new goals or delivery methods such as intranasal boosters the panic coronavirus vaccines. “It’s been a guessing game of what the virus will do next, and those who receive a fourth dose in the near future will still be eligible for any new formulations from mid-October or thereabouts.” These new vaccine technologies can potentially elicit a stronger immune response due to the fact that they stimulate another arm of the immune system or target several different coronaviruses altogether. “We don’t know when these paradigm-changing vaccines will be available, but it could be a while — particularly if we wait as seems prudent to get really good data on their efficacy and safety,” Naylor said. “To me, this reality and the continued spread of the BA.5 together argue for continuing with a fourth shot, even if it’s more of the same with modest marginal returns.” WATCHES | Summer’s COVID-19 wave sparks concerns:
The summer wave of COVID-19 is cause for concern
The rising cases have prompted some provinces to declare a seventh wave of COVID-19, which is causing concern for many health care workers. But Chagla said Canadians need to start thinking about the protection offered by COVID-19 vaccines differently than before. There will be “limits” to what they can and cannot do in both…
