How do you decide on the best vaccination strategy for the fall? | Coronavirus

1. Do we need a new vaccination campaign?

According to Benoît Barbeau, Professor at the Department of Biological Sciences at UQAM and an expert in virology, we have to prepare for several scenarios. We don’t know what to expect in the fall, he warns. Everything can surprise us. Omicron was a glaring example.

Firstly, we must take into account that for many people it has been several months since their last dose.

If the vaccine remains effective in preventing serious complications, it has nevertheless lost some of its effectiveness with the emergence of new variants, says André Veillette, an immunologist and researcher at the Montreal Clinical Research Institute.

It’s like the common cold: a vaccine doesn’t protect you for life. The type of immune protection decreases over time. »

A quote from André Veillette, immunologist

In addition, we know that 55% of Canadians have not received their booster (third) dose, which is still necessary to cope with Omicron.

It should also be remembered that current vaccines are based on the original strain of SARS-CoV-2.

However, there has been significant genetic evolution of the virus since the pandemic began, and researchers believe the mutation is ongoing.

While the Alpha and Delta variants have genetic mutations close to the original strain discovered in 2020, the Omicron variant is vastly different.

In addition, since the appearance of Omicron, there have been many subvariants, such as BA.2, BA.3, BA.4, and BA.5. Each has very different mutations from each other.

In addition, according to a study (New window) – not peer-reviewed – from the University of Tokyo, the sub-variants BA.4, BA.5 and BA.2.12.1 manage to partially thwart the immunity granted (New window) through vaccinations and through infections.

And unlike the BA.1 and BA.2 variants, which infected the upper respiratory tract and caused milder infections, these new subvariants attack the lungs more severely, as did the Alpha and Delta variants.

Overall, our analysis suggests that the risk of these Omicron subvariants, particularly BA.4 and BA.5, to global health is potentially greater than that of BA.2write the authors.

Nine million Canadian adults have been infected with Omicron, according to Catherine Hankins, co-chair of the COVID-19 Immunity Task Force. But this mass infection won’t be enough to prevent a new wave being caused by the Brotherhood of Omicron, she says. Many people have been infected two or even three times since last December.

Additionally, according to the latest federal data in early June, more than 20% of infections were caused by BA.4 or BA.5. According to modeling experts interviewed by CBC (New window)these variants now account for up to 50% of new cases.

2. So should we wait for new versions of vaccines or use the current vaccine?

At the moment, the authorities have two options, says André Veillette: continue using the original vaccine or wait for a vaccine adapted to the Omicron variant.

Last week, the World Health Organization (WHO) recommended making the next vaccine based on the Omicron variant.

Why Omicron and not another variant? The WHO states that most of the latest genetic mutations have occurred in the Omicron lineage and that this is the dominant strain at the moment.

Benoît Barbeau believes that such a modified vaccine would be welcome and better suited to the variants currently circulating. It would be an adapted vaccine representing not only the Omicron variant but also the strain [originelle] from Wuhan.

Many hope that Moderna or Pfizer will soon produce a vaccine that combines the original strain of SARS-CoV-2 with the Omicron variant.

However, Mr Veillette states that it is not yet clear whether these new bivalent vaccines will be better than current vaccines. The Omicron subvariant that [les compagnies pharmaceutiques] The BA.1 is used. But we already have several versions of Omicron that are already very different from BA.1.

Preliminary results (New window) Clinical trials for Moderna’s bivalent vaccine (targeting both the Omicron variant and the original strain), presented in early June, show that levels of neutralizing antibodies have increased eight-fold. The company also says the vaccine appears to be effective against subvariants BA.4 and BA.5, but didn’t elaborate.

Pfizer-BioNTech was introduced last week (New window) that his two vaccines modified according to the Omicron variant a significantly higher immune response than the currently available vaccine.

The candidate suitable for Omicron increases the amount of neutralizing antibodies between 13.5-fold and 19.6-fold, depending on the dose administered.

The bivalent vaccine candidate (Omicron and original strain) increases the number of neutralizing antibodies by 9.1 to 10.9 fold, depending on the dose administered.

However, these vaccines are less effective for subvariants BA.4 and BA.5, Pfizer says.

To add to the uncertainty, it’s always possible that new variants could emerge before these Omicron-specific vaccines arrive. Even if that scenario materializes, Mr Barbeau believes this new version of the vaccines would still offer more robust immunity against SARS-CoV-2.

According to Mr Veillette, the best way at this stage is to plan a vaccination campaign with the first vaccines, with the option of offering new vaccines if they become available.

There is clearly nothing better at the moment. People should be encouraged to get an extra dose. »

A quote from André Veillette, immunologist

3. Can these new vaccines be produced in time for the fall?

Of course there is a difference between what we want as a vaccine and what we can produce before the autumn, says Mr Barbeau. The process can be lengthy and complicated due to constant mutations in the virus.

If we take the example of the flu, it usually strikes predictably and seasonally. A global surveillance network helps the World Health Organization (WHO) decide each year which vaccine strains to include in the annual vaccine. In particular, we are monitoring the flu season in the southern hemisphere to better predict what is likely to hit the northern hemisphere.

This allows each country to choose their preferred variety. Vaccine manufacturers then have about six months to prepare.

With COVID-19, the virus is not yet spreading cyclically. In addition, SARS-CoV-2 mutated five times faster than the flu virus. A new strain of influenza usually emerges every 3 to 5 years. In the case of SARS-CoV-2, there were already five interesting variants.

This makes it difficult for pharmaceutical companies to quickly change their formulation and create new versions of their vaccine.

By the time we arrive with a vaccine adapted to one variant or subvariant, it is very likely that we have moved on to the next variant.says Mr. Barbeau, adding that it is not a waste of time.

We’re trying to have the best possible version of the vaccine that will give us protection, even if it’s not perfect. »

A quote from Benoit Barbeau, expert in virology

When the first COVID-19 vaccines became available in 2021, pharmaceutical companies boasted that they could deliver a new version of the vaccine within 100 days.

Mr Barbeau thinks that’s a bit too optimistic a promise. It’s not impossible, but it’s far from possible. Yes, they can quickly change the recipe because we only change the RNA; it’s a more flexible technology. But it is still necessary to make these cans.

According to Moderna, its vaccine will be ready by August and will be available for distribution in September or October. Pfizer has submitted its data to the FDA, which will have to decide in the coming weeks whether and how this modified vaccine adapted to Omicron will be approved. It is not clear when these vaccines will be approved in Canada.

4. Will there be intranasal or universal vaccines?

As for universal vaccines – which would protect people from multiple coronaviruses – Mr Veillette and Ms Hankins say we still have a few years to wait.

It’s a dream from a long time agoadds Mr. Veillette.

As for vaccines given through nasal spray, which could help reduce transmission of the virus, Veillette said there’s still no clear evidence it works. He adds that these vaccines are not necessarily easier to administer.

For now, says M. Veillette, People have to be content with conventional vaccinesnoting that the vaccines currently available still represent a significant scientific advance.

5. When should a new vaccination campaign start?

The timing of giving new doses is very important and depends on several factors. If the vaccine is given too early, immunity could fade before a winter wave begins; If administered too late, the virus could easily spread in a population that no longer has strong enough immunity.

what we see [pour Omicron] When it comes to vaccination protection, the number of vaccinations is less important than the date of your last vaccinationSarah Otto, an expert in modeling and evolutionary biology at the University of British Columbia, told CBC.

The longer you wait for the vaccine, the newer it is and the more effective it will be in the next wave. So you don’t want to get it months before the next wavesays Ms. Otto.

Some provinces, such as Quebec, announced a new vaccination campaign in September. It may be a little early, according to Mr Barbeau, but perhaps a necessary evil.

We are not in an established cycle with this virus. There are still many unknowns. »

A quote from Benoît Barbeau, expert in virology

On the one hand, an increase in cases is expected due to the return to school and work in September. On the other hand, cases also increased in December and January in the last two years.

If we waited until October or November we would have better protection in winter. Otherwise, a booster dose may need to be given in wintersaid Mr. Barbeau.

It is above all the evolution of the epidemiological situation that should dictate the start of new vaccination campaigns, Mr Barbeau believes. If the epidemiological situation is stable, then we should not rush to vaccinate everyonehe said, adding that authorities need to remain flexible as new surges are possible at any time.

In addition, there is an upswing possible in the summer with the arrival of the new BA.4 and BA.5 variants of the Omicron family, the Federal Health Agency warns.

6. Should the vaccine be offered to everyone?

According to Mr Barbeau, we should first prioritize vulnerable people and specific age groups. For example, Quebec has announced that people over the age of 60, people over the age of 5 who are immunocompromised, are on dialysis or living with a chronic disease, medical workers, pregnant women and adults living in remote regions can receive an additional dose at the end of summer.

But he adds that when there is a huge surge in infections, we should not hesitate to offer the vaccine to the entire population.

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