How to decide the best vaccination strategy for the fall? | Coronavirus


1. Will we need a new vaccination campaign?

According to Benoît Barbeau, professor in the Department of Biological Sciences of UQAM and an expert in virology, we need to be prepared for different scenarios. We do not know what awaits us in the fall, he warns. Everything can surprise us. Omicron was a prime example.

First, we must take into account that, for many people, their last dose was several months ago.

While the vaccine remains effective at preventing serious complications, it has still lost some of its effectiveness with the arrival of new variants, says André Veillette, immunologist and researcher at the Montreal Clinical Research Institute.

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

A quote from André Veillette, immunologist

Furthermore, we know that 55% of Canadians have not received the booster dose (third dose), which is still needed to deal with Omicron.

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

However, since the start of the pandemic, there has been a substantial genetic evolution of the virus, and researchers believe it has not finished mutating.

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

Also, since Omicron appeared, there have been many sub-variants, such as BA.2, BA.3, BA.4 and BA.5. Each has very different mutations from each other.

Also, according to a study (New window) – not peer-reviewed – of the University of Tokyo, the sub-variants BA.4, BA.5 and BA.2.12.1 manage to partially nullify the immunity conferred (New window) from vaccines and infections.

And unlike the BA.1 and BA.2 variants which infected the upper respiratory tract and caused milder infections, these new sub-variants attack the lungs more, as is the case with the Alpha and Delta variants.

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

According to Catherine Hankins, co-chair of the COVID-19 Immunity Task Force, nine million Canadian adults have been infected with Omicron. But this mass infection won’t be enough to prevent a new wave from the Brotherhood of Omicron, she says. Since last December, many people have been infected two or even three times.

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

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

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

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

Why Omicron rather than another variant? WHO explains that most of the latest genetic mutations have occurred in the Omicron line and that this is the dominant strain at the moment.

Benoît Barbeau believes such a modified vaccine would be welcome and more suitable for the variants currently in circulation. It would be an adapted vaccine with representativeness not only of the Omicron variant, but also of the strain [originelle] from Wuhan.

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

Mr. Veillette specifies, however, that it is not yet clear whether these new bivalent vaccines will be better than the current vaccines. The Omicron sub-variant which [les compagnies pharmaceutiques] the use is the BA.1. But we already have several versions of Omicron which 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 neutralizing antibody levels have increased eightfold. The company also says the vaccine appears to be effective against the BA.4 and BA.5 subvariants, but hasn’t elaborated.

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

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

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

In the case of the BA.4 and BA.5 sub-variants, however, these vaccines are less effective, Pfizer says.

To increase the uncertainty, it is always possible that new variants may appear even before the arrival of these Omicron-specific vaccines. Even if this scenario materializes, Barbeau believes this new version of the vaccines would still offer more robust immunity against SARS-CoV-2.

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

There is clearly nothing better right now. 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’s a difference between what we want to have as a vaccine and what we’re able to produce before the fall, says Barbeau. The process can be long and complicated due to the constant mutations of the virus.

If we take the example of the flu, it usually strikes in a predictable and seasonal way. A global surveillance network helps the World Health Organization (WHO) decide each year which vaccine strains to incorporate into the annual vaccine. In particular, we monitor the flu season in the Southern Hemisphere to better predict what could affect the Northern Hemisphere.

This allows each country to choose which variety they prefer. Vaccine manufacturers then have about six months to prepare.

In the case of COVID-19, the virus is not yet spreading cyclically. Furthermore, SARS-CoV-2 mutated five times faster than the flu virus. A new flu strain normally appears every 3-5 years. In the case of SARS-CoV-2, there have already been five variants of interest.

This makes it harder for pharmaceutical companies to quickly change their recipe and produce new versions of their vaccine.

When we come up with a vaccine adapted to one variant or sub-variant, 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 try to have the best possible version of the vaccine that gives us protection, even if it’s not perfect.

A quote from Benoit Barbeau, virology expert

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

Mr. Barbeau thinks it was a little too optimistic a promise. It is not impossible, but it is far from possible. Yes, they can change the recipe quickly because we only change the RNA; it is a more flexible technology. But it is still necessary to produce these doses.

Moderna says 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 the Micron will be authorized. It is unclear when these vaccines will be authorized in Canada.

4. Will there be intranasal or universal vaccines?

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

It’s a long time ago dreamadds Mr. Veillette.

As for nasal spray vaccines, which could help reduce transmission of the virus, Veillette says there is still no clear evidence that they work. He adds that these vaccines are not necessarily easier to administer.

For now, says M. Veillette, people will have to make do with conventional vaccinesrecalling that the vaccines currently available still represent a significant scientific advance.

5. When should a new vaccination campaign start?

The timing for the administration of new doses is very important and depends on several factors. If the vaccine is given too early, immunity may wane before a winter wave begins; if given too late, the virus could easily spread to a population that no longer has robust enough immunity.

what we see [pour Omicron] with vaccine protection, it is not so much the number of doses that is more important than the date of the last doseSarah Otto, an expert in modeling and evolutionary biology at the University of British Columbia, told CBC.

The longer you wait to get 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 Mrs. Otto.

Some provinces, such as Quebec, announced a new vaccination campaign in September. According to Mr. Barbeau, it may be a little early, 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, virology expert

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

If we had waited until October or November, we would have better protection during the winter period. If not, you may need to give a booster dose in the wintersaid Monsieur Barbeau.

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

Also, a surge is possible during the summer with the arrival of the new variants BA.4 and BA.5 of the Omicron family, warns the federal public health.

6. Should the vaccine be offered to everyone?

According to Mr. Barbeau, we should first prioritize vulnerable people and certain age groups. For example, Quebec announced that people aged 60 and over, people aged 5 and over who are immunosuppressed, on dialysis or living with a chronic illness, health care workers, pregnant women, and adults living in isolated regions will be able to receive an additional dose at the end of the summer.

But he adds that we shouldn’t hesitate to offer the vaccine to the entire population if there is a huge increase in infections.


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