Faced with changes in the coronavirus, which vaccines to bet on?

Researchers believe that it is necessary to bet on vaccines easy to adapt since the coronavirus is transformed more and more at the risk of weakening the current vaccines.

“I am not sure that we will not have to repeat a vaccination campaign in October”, warns to AFP Yves Gaudin, virologist at the National Center for Scientific Research (CNRS) in France.

Because, for several months, new strains of the virus at the origin of Covid-19 have emerged, different from the versions against which the first vaccines were developed.

One of them, the so-called British variant, has been the majority among the new contaminations in France since last week. Admittedly, this strain seems, in its current form, to pose a problem of increased contagiousness rather than resistance to vaccines.

Less efficiency compared to other variants

But faced with other variants, in particular the so-called South African one, the first studies indicate a lower effectiveness of the main vaccines currently on offer.

What type of vaccine can we most rely on in this changing situation? For researchers interviewed by theAFP, the challenge is first of all to quickly adapt those already developed.

Or “There are formats that are faster and more easily adaptable”, emphasizes Sylvie Van der Werf, virologist at the Institut Pasteur in France. “Clearly, these are the messenger RNAs. “

The Pfizer / BioNTech and Moderna vaccines, therefore: they directly inject RNA sequences that lead cells to manufacture proteins present in the coronavirus in order to accustom the immune system to them. These sequences can be very quickly synthesized in the laboratory.

In contrast, the AstraZeneca and Johnson & Johnson vaccines use the technique of “Viral vector”. It also integrates genetic material into cells but taking as ” shuttle bus “ a pre-existing virus, otherwise different from the coronavirus.

It takes longer to develop. In little more than a month, Moderna launched clinical trials for a new vaccine, while AstraZeneca warned that such work would take it six months – a quick turnaround by standard.

Most “It is not sure that there is such a big difference between messenger RNAs and viral vectors, once you take into account the large-scale production”, put into perspective withAFP Julian Yang, virologist at the UK University of Leicester.

Vaccines inactivated to “reflect mutations”

Messenger RNA vaccines indeed require maintenance at a very low temperature, which complicates the steps following the synthesis of the active principle.

Innovative, these two categories are in any case much faster to redevelop than conventional vaccines, says “Inactivated”.

However, the British government has high hopes for these vaccines to respond to the emergence of new strains.

Against the Covid-19, they are not yet approved in Europe but one of them, developed by Valneva, should be distributed in the United Kingdom by the autumn.

While messenger RNA and viral vector vaccines focus on a small part of the virus – the S protein, known as « Spike » – inactivated vaccines use the coronavirus as a whole to develop the immune response.

This “Gives much more chance to reflect mutations”, judged Secretary of State Nadhim Zahawi in early February before British parliamentarians, judging that this vaccine could therefore be “Incredibly efficient”.

Hope for a “universal” vaccine

Count on a vaccine that does not need to be readjusted often? The idea leaves researchers interviewed by theAFP, who consider it very hypothetical.

“For now, this has not been demonstrated”, believes Étienne Decroly, specialist in emerging viruses with the CNRS, seeing the hope of a vaccine “Universal” which no longer requires any adaptations.

“We have been trying to do it for ten years against the flu; if unfortunately it has not yet come to fruition, we can say to ourselves that things are not that simple ”, he notes, noting that over time viruses will tend to mutate in a direction that eludes existing vaccines anyway.

Worse, it could be counterproductive to rely too much on inactivated virus vaccines.

“Of course, that induces a very broad response, but what we want is first of all a good response against the Spike protein”, says Mr. Gaudin.

Or “Inactivating the virus can sometimes damage the protein”, potentially limiting the effectiveness of the vaccine, he warns.

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