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COVID: The next bivalent chemotherapy vaccine in the fight against the virus

The decline in COVID-19 projections makes another boosted vaccine campaign likely, but many questions remain about how the virus will continue to evolve and what precautions to take. protection that a new injection can provide.

Several vaccine manufacturers are racing to develop formulations that take into account the more infectious Omicron variant that is currently driving cases, while policymakers are laying the groundwork for a other large-scale vaccines.

Much of this depends on the expectation that the so-called two-shot shot could reduce the risk of future spikes when flu season kicks in and ease the pressure on a strained health care system. .

The National Advisory Committee on Immunization last week released interim guidance for the fall program it says is most important for older adults and those at high risk for severe COVID-19. It also notes that while the vaccine’s protection against symptomatic disease declines over time, protection against severe disease is better maintained.

In the United States, Food and Drug Administration advisers said last week that the fall booster should contain some version of the Omicron variant.

The NACI has stopped short of urging a specific formulation pending further evidence, but does say that a two-way dose could encourage absorption in the fall.

This is the next phase in the fight against COVID-19.

WHAT ARE THE BACK PATTERNS?

Existing COVID-19 vaccines are monovalent – adapted only to the original novel coronavirus. The proposed chemotherapy vaccines target specific mutations in the mutant protein found in both the older and newer Omicron lines, which in turn have given rise to several infectious sub-variants that dominate the infections. coincides today.

In essence, a dual-valued vaccine is a split between the old “original” mRNA sequence and the new one, said infectious disease expert Dr Zain Chagla.

“For example, for example, Moderna’s two vaccines are 25 mcg of the old vaccine, 25 mcg of the new vaccine,” he said.

The fundamentals are well established with the flu vaccine, says immunologist and University of Toronto professor Tania Watts.

“With the flu, we make three or four different variants. It’s just a mix, and RNA vaccines are easy to mix and match. In theory, we could have 10,” Watts said. targeted variant)”.

“And I think that’s the future. People are working towards getting a universal vaccine.

IS IT TOO LATE FOR A VACCINE OMICRON?

Experts say Canada has suffered a third wave of Omicrons, which could then pose a threat from a new COVID-19 variant, but that doesn’t necessarily make the refined Omicron vaccine obsolete. if it doesn’t land until crash.

Dr Volker Gerdts, director and chief executive officer of the Vaccines and Infectious Diseases Foundation, says the best strategy is to provide as broad a protection as possible.

“That’s why some of these bivalent vaccines still have the original strain, and then have Omicron or Delta added to it,” says Gerdts.

“The whole goal is to have a variety of different types in your vaccine to provide broad-spectrum protection.”

Part of the difficulty in evaluating new vaccines, he said, is evaluating them against variants that don’t even exist.

“If we have this vaccine representative from very different strains or variants, then we can assume that we also get broad protection against variants in the vaccine,” he said. future,” he said.

Pfizer Canada and Moderna Canada both say their mRNA platforms allow for rapid updates to address new variants if needed.

But it’s possible that “divalent boosters could provide broad protection against a number of different variants, even those they weren’t specifically designed to combat,” said Shehzad Iqbal, director Medical of Moderna Canada, said by email.

WHAT CAN VACCINES PATIENTS DO?

Chagla, a professor at Hamilton’s McMaster University, says there’s some uncertainty here.

The evidence to date is that they can increase antibody levels even more than previous doses. But he says there is no clinical data that illustrates exactly what that means: Does it provide longer protection from symptomatic disease? Even more protection against hospitalization? How long do the effects last? Will they weaken over time?

“There are no guarantees with this upcoming booster,” says Chagla.

“My guess is that it will probably prolong the benefit for symptomatic infections beyond eight weeks, nine weeks, 10 weeks.”

He suspects they will work like current COVID-19 shots: the antibodies produced break down over time and people can get infected again.

Complicating matters, Chagla added, is that the virus continues to evolve.

WHEN WILL THEY COME?

Moderna Canada said it submitted its bivalent booster candidate to Health Canada on June 30 for regulatory approval. Iqbal said the proposed update is a 50 mcg dose containing the original vaccine, called Spikevax, and a vaccine candidate that targets Omicron.

“While we cannot speculate on the timing of Health Canada’s review, our goal is to have Omicron-containing divalent boosters available by early fall 2022,” Iqbal said.

Pfizer Canada also said it plans to seek approval for another COVID-19 vaccine.

“We are currently in discussions with Health Canada to prepare to submit our available data, including data for constructs including the Omicron BA.1 or BA.4/5 subvariables,” the company said. said by email.

WHAT IS CHALLENGE?

If the two shots are ready for the fall, infectious disease expert Dr. Isaac Bogoch hopes we can run three vaccine programs simultaneously: one booster program, one COVID vaccine program. -19 for children under the age of six if they are also approved; and annual flu vaccination program.

Bogoch, a professor at the University of Toronto, said: “One of the challenges is that in much of the country, a lot of the infrastructure for mass vaccination has been dismantled.

“Vaccines are now mainly offered in traditional locations such as primary care clinics, community health clinics and pharmacies. So it’s probably going to be a very busy time. .”

Chagla added that there are a lot of factors that are needed to ensure a smooth vaccine rollout, as seen in the difficult days when Canada first pushed for needles in hand: “It’s not as simple as that. droplet vaccine and everyone has the right to use it, right?”

“You have to scale up, and this often takes people away from their day jobs, away from doctors, from patients and nurses and other valuable staff from healthcare,” says Chagla. “.

Such campaigns should be arranged to deal with the increased risk of infection, he added, making autumn possibly the best time to boost population immunity, he added. as indoor and seasonal gatherings increase.

WHAT NEXT?

Bogoch and Chagla both point to solid advances in technology that could shape the coming years, including work on developing a needle-free nasal vaccine.

“And those could be very promising because it really focuses on what’s called the mucosal immune system,” Bogoch said. And that could allow us to better prevent infections in the first place.

Along with Gerdts, they also advertise an effort to create a pan-coronavirus vaccine that can provide protection against many coronaviruses.

Such a product could include structures from various members of the coronavirus family, Gerdts said – not only SARS-CoV-2 that causes COVID-19, but possibly Middle East respiratory syndrome, also known as MERS, and another common respiratory coronavirus.

“The farther members are from each other in terms of whether you have your vaccine, the greater the protection against the new variants derived from them,” said Gerdts, who was due to attend a meeting. meeting in Washington on Thursday and Friday due in part. National Institutes of Health to decide how to protect against future variants.

“If a virus mutates and evolves further, it has to start somewhere and continue with existing viruses – but pick some viruses that are very far apart so you’ve evolved pretty much already – chances are you come across all these new viruses with mutants in between.”

Such a vaccine is still many years away, he added.

“Much of this is really about predicting what tomorrow’s pathogen might be.”


This report by the Canadian Press was first published on July 7, 2022.

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