Paris (AFP)

Several new studies seem to confirm the first clues from scientists: the South African variant risks at least partially escaping the expected protection of vaccines against Covid-19, unlike the English variant, against which the vaccine from BioNTech / Pfizer seems effective .

While hospital systems are already overloaded in many countries around the world, several more transmissible variants detected in the United Kingdom, South Africa and Brazil have worried the international community for a few weeks.

Initial elements seemed to show at least an efficacy of the vaccine from BioNTech / Pfizer, the first to arrive on the market, against one of the mutations shared by the three variants, N501Y.

This mutation is located at the level of the spike protein of the coronavirus, the point which is on its surface and allows it to attach to human cells to penetrate them, thus playing a key role in viral infection.

But the fears came mainly from the E484K mutation, also located on the Spike protein, and shared only by the South African and Brazilian variants.

Laboratory tests have already shown that this mutation seemed capable of reducing the recognition of the virus by antibodies, and therefore its neutralization.

A study by South African researchers posted online Wednesday, and not yet evaluated by other scientists, goes further.

It concludes that the South African variant as a whole "is largely resistant to neutralizing antibodies elicited in response to infection by previously circulating strains".

Thus, the risk of reinfection by this variant is "important", underlines the study.

And these data have "implications for vaccine efficacy," particularly because current vaccines are "primarily based on an immune response to the Spike protein."

"This is a problem that worried many of us: that new variants of Sars-Cov-2 escape the immune response in addition to their greater transmissibility", commented on Twitter Kristian Andersen, immunologist at the institute Scripps research.

"Impossible to water down things: this is not good news," he added.

- Adapt vaccines -

In an attempt to counter these threats, the authors of the study on the South African variant call for identifying new "targets" for these vaccines which would be less subject to mutations than the Spike protein, and for developing "urgently" platforms to adapt vaccines if necessary.

The messenger RNA vaccines from BioNTech / Pfizer and Moderna, which have received marketing authorizations in several countries around the world, allow a priori a relatively rapid adaptation.

The German laboratory BioNTech has also assured to have the technology to produce if necessary a vaccine against new variants in six weeks.

If the results of the South African study are confirmed, "we must determine a production schedule and regulatory steps to adapt the strain used in the vaccine," Trevor Bedford of the Fred Hutch Research Center commented on Twitter on Wednesday.

Even if the 501Y.V2 variant is "still largely confined to South Africa", it "could spread more widely in the coming months", he added, betting on the need to adapt the " strain "of the vaccine in the fall of 2021.

"It's part of human nature to love being scared, but we must not panic," said James Naismith, of the University of Oxford, quoted by the organization Science Media Center.

Especially since new data posted online Wednesday seems to confirm that the English variant, which has already largely crossed borders, would be very receptive to the vaccine from BioNTech / Pfizer.

According to two separate studies, one by BioNTech / Pfizer researchers, the other by researchers from British and Dutch universities, the antibodies of former Covid-19 patients largely make it possible to neutralize the English variant, even if the neutralizing power can be slightly reduced.

It is thus "improbable" that the English variant "escapes the protection" of this vaccine, concludes the BioNTech / Pfizer team.

Against the English variant, "vaccines should be very effective and vaccination coverage is a priority," said on Twitter Professor Ravi Gupta of Cambridge University, one of the authors of the other study.

© 2021 AFP