Tuesday, May 17

Covid-19. Omicron: why Pfizer and BioNTech are testing a new vaccine formula

The epidemic is still blazing, despite high vaccination coverage: while current vaccines remain effective against most severe forms of Covid-19, they prevent viral transmission too little.

What is it about?

The Pfizer-BioNTech alliance this week began recruiting volunteers for a clinical trial which aims to test the safety and the immune response induced by their new vaccine against Covid-19 specifically dedicated to the Omicron variant.

At the beginning of January, the boss of the American laboratory Pfizer, Albert Bourla, declared that he was ready to request authorizations for this new vaccine from March.

Why a new formula?

While current data indicate that booster doses of the original vaccine protect against severe forms of Omicron, it only very imperfectly suppresses viral transmission – especially in the absence of a booster dose.

The company says it prefers to act on the side of caution:

We recognize the importance of being prepared in the event that this protection diminishes over time, and to help deal with Omicron and other variants in the future.

Kathrin Jansen, Head of Vaccines at Pfizer

In fact, protection wanes over time, whether it’s the initial vaccination or the booster dose – and that’s a classic phenomenon. It remains to be seen after how long, and whether the drop in the number of antibodies has an effect on protection against serious forms, or only on a possible infection.

And faced with the Omicron variant, it is accepted that the protection conferred by current vaccines is less good.

This study takes place within the framework of our scientific approach which aims to develop vaccines targeted against the variants which manage to develop similar levels of protection against Omicron, as for the variants which appeared earlier, but with a longer duration of protection.

Ugur Shain, CEO of German company BioNTech

How many people involved?

The clinical trial involves 1,420 people between the ages of 18 and 55. It will not include people over 55, because its purpose is only to raise the immune response of participants, not to estimate the effectiveness of the vaccine, details a spokesperson for Pfizer.

Trial participants will be divided into three groups.

The first includes people who have received two doses of the Pfizer-BioNTech vaccine in the previous 90 to 180 days, and who will receive one or two injections of the new tested serum.

The second group will be made up of individuals who received their booster dose, during this same period, and who will receive either a new dose of the initial vaccine, or a dose of the vaccine specifically designed against the Omicron variant.

Finally, the third includes people who have not received any vaccine against Covid-19 and who will receive three doses of the one that specifically targets Omicron.

Why is it easier with messenger RNA?

The initial vaccine developed by Pfizer and BioNTech was the first authorized in Western countries, in December 2020. It had been shown to be very effective against severe forms – in accordance with the specifications – but also against infections. On this last point, this is no longer the case as new variants appear.

Its design, based on messenger RNA technology, allows it to be relatively easy to modify and update to follow the evolution of mutations specific to new variants. This technology won the French Nobel Prize in 1965, and had been studied for vaccines since the 1990s.

In the context of a pandemic, research, boosted by mobilization and large-scale funding, has overcome the last persistent problems with this technology.

Unlike “conventional” vaccines, messenger RNA vaccines do not incorporate a virus, whole or not, living or not, but a piece of its genetic code. This makes them easier to modify, but also to produce on a large scale. They are also reputed to be safer, with fewer side effects. Finally, they do not require adjuvants.

The clinical trials of this vaccine, carried out in the emergency of an unprecedented pandemic since the Spanish flu of 1918, brought together the largest number of volunteers ever gathered.

What risk with other variants?

Several countries have started to see a drop in cases due to the wave caused by Omicron, the most transmissible variant detected at this stage, even if the number of contaminations in the world continues to climb.

The concern today relates to the appearance of a sub-variant of Omicron, BA.2, whose immune escape would be higher. It is already the majority in Denmark, and weighs for a third of the cases in the Berlin region.

The balance is delicate: future vaccines will have to “cast” wide enough to encompass these new avatars of the virus, which will appear inexorably, while being specific enough so as not to trigger a poorly targeted immune response in the human body.


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