COVID-19: How bivalent vaccines help protect against new variants

Fall PredictionCOVID-19Waves increase the likelihood of another booster vaccine campaign, but how the virus continues to evolve and new shots There are many questions about what kind of protection can be provided by.

Several vaccine manufacturers are competing to develop formulations that take into account the more infectious variants of Omicron that are currently promoting the case.

Much of this rests on the expectation that so-called divalent shots will slow down potential future spikes as the flu season begins and reduce pressure on a tense healthcare system.

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last week, the National Advisory Board on Immunity was most important for the elderly and those at high risk of severe COVID-19. We have announced provisional guidelines for the fall program that we mentioned. It was also noted that vaccine protection against symptomatic disease declines over time, but protection against severe disease is better maintained.

In the United States, the Food and Drug Administration adviser last week and the fall booster had several versions of the Omicron variant. Should be included.

NACI stopped encouraging certain prescriptions while waiting for further evidence, but said divalent shots could promote intake in the fall.

Let's take a look at the next stage of the battle with COVID-19.

With bivalent vaccine What is.

The currently available COVID-19 vaccine is monovalent and has been tuned for the original coronavirus only. The proposed bivalent vaccine targeted specific mutations in the peplomer found in both old and new Omicron strains, producing several infectious subvariants that themselves dominate infection today.

In essence, the bivalent vaccine is split between the old "original" mRNA sequence and the new sequence, says infectious disease specialist Dr. Zain Chagla.

"For example, Moderna's divalent is 25 mcg of old vaccine, 25 mcg of updated vaccine." He says.

The basic principles have already been established for influenza vaccines, says immunological professor Tania Watts of the University of Toronto.

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"Influenza performs 3 or 4 different variations. It's just a mixture and RNA vaccines mix very easily. In theory, you can have 10 (targeting variants), "says Watts.

"And I think that's the future. People are looking for a universal vaccine."

is too late for the Omicron vaccine.

According to experts, Canada is already on the verge of a third Omicron wave, which could be followed by the threat of a new COVID-19 variant, but not necessarily in Omicron. Adjusted vaccines are not obsolete. If you do not land until autumn.

Dr. Vaccine and Infectious Disease Organization Director and CEO. Volker Gerdts states that the best strategy is to provide the widest possible protection.

"This is why some of these so-called bivalent vaccines still contain the original strain, plus Omicron or Delta," Gerdts says.

"The overall goal is to include multiple different types of vaccines to provide broad protection.

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Part of the difficulty in evaluating new vaccines is to evaluate them against mutants that don't even exist, he says.

"If the expression in this vaccine contains very different strains or different mutants, we can assume that broad protection will be available for future mutants," he says. increase.

PfizerCanada and ModernaCanada each state that the mRNA platform allows rapid updates to address new variants as needed.

However, "Bivalent boosters can provide broad protection against several different variants, even if they are not specifically designed to fight," Moderna Canada said. Shehzad Iqbal, medical director of the company, said in an email.

What you can do with a bivalent vaccine.

There is uncertainty here, says Chagra, a professor at McMaster University in Hamilton.

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That evidence far they can raise antibody levels even further than previous doses. But he says there are no clinical data that show exactly what that means. Will it lead to longer protection against symptomatic treatment? More protection against hospitalization. How long will the effect last? Will they decline over time?

"There is no guarantee that this booster will come," says Chagla.

"My guess is that the effects of symptomatic infections will probably be extended by 8 weeks, 9 weeks, 10 weeks or more."

He is currently COVID-19. I think it works much like a shot. The induced antibody disintegrates over time and people can be infected again.

The complex problem is the fact that the virus keeps evolving, Chagla adds.

When will you arrive?

Moderna Canada states that it submitted a bivalent booster candidate to Health Canada on June 30 for regulatory approval. Iqbal states that the proposed update is a dose of 50 mcg containing the original vaccine known as Spikevax and a vaccine candidate targeting Omicron.

"We can't guess when the Health Canada review is, but our goal is divalent, including Omicron. It's about making boosters available in early fall. 2022, "says Ikubal.

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

"We are currently discussing with Health Canada about preparing to submit available data, including data for constructs containing Omicron BA. 1 or BA. 4/5 subvariants," the company said. It is stated in the email.

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What is the challenge?

If a divalent injection is ready for fall, infectious disease expert Dr. Isaac Bogotch has a booster program, COVID-19 vaccine for children under 6 years of age. We expect to be able to run the program's three simultaneous vaccine programs. They are also approved. Annual influenza vaccine program.

“One of the challenges is the removal of much of the infrastructure for mass vaccination in many countries,” says Professor Bogoch of the University of Toronto.

"Vaccines are currently mainly administered in traditional locations such as primary care clinics, public health clinics and pharmacies, so it will probably be a very busy time."

Chagla adds that there are many moving parts to ensure smooth vaccine deployment. Access, that's right.

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"Need to scale up, often people away from day-to-day work , Doctors are away from patients, nurses, etc. Valuable staff away from healthcare, ”says Chagra.

Such campaigns should be timed to address the increased risk of infection. This may be the best time to replenish herd immunity in the fall, before more indoor and seasonal gatherings.

What's next?

Both Bogoch and Chagla point to steady advances in technology that may shape the next few years, including the work of developing needleless intranasal vaccines.

"And they may be very promising because it really focuses on what is called the mucosal immune system, and it allows us to better prevent infection in the first place. "Maybe," says Bogok.

Gerdts, they also Produces protection against multiple types of coronavirus.

According to Gerdts, such products include not only SARS-CoV-2, but also a variety of coronavirus families. Member structure may be included. COVID-19, as well as Middle East Respiratory Syndrome, probably also known as Middle East Respiratory Syndrome, and another common respiratory coronavirus.

"The farther a member is included in the vaccine, the greater the level of protection against new variants that emerge from the member," he said at a conference in Washington on Thursday. Was Gerdts said. Friday was partially organized by the National Institutes of Health to determine how to protect from future variants.

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"The virus mutates and evolves further, so it needs to start somewhere, so it should be used with existing viruses, but if you choose one that is very far from each other. , Already quite evolved. It has the potential to catch all of these new variants. It will emerge in the meantime. "

Such vaccines are still years away, he adds. increase.

"Most of this is really about predicting what the pathogens of tomorrow will be today."

This report by the Canadian Press is 2022. First published on July 7, 2014.

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