Washington (AFP)

Moderna's vaccine against Covid-19 remains effective against variants of the coronavirus, in particular the British, but a reduction in protection against the South African variant has however been observed, the American biotechnology company announced on Monday.

Moderna therefore decided to launch, "as a precaution", trials aimed at testing an additional dose developed specifically against the South African variant.

Experts expect Moderna's vaccine, called mRNA-1273, "to protect against variants detected so far," the company said after testing of blood samples from eight people who received the drug. both doses of the vaccine, and two primates equally immune.

"The study did not show a significant impact on the titers (levels, NDLR) of antibodies against the B.1.1.7 variant compared to previous variants," Moderna explained of the British variant.

In contrast, a "six-fold reduction" in antibody levels against the South African variant (B.1.351) was observed.

"Despite this reduction", the antibody levels "remain above what is expected as necessary to provide protection", wanted to reassure Moderna.

The results of the trials, conducted in collaboration with the American National Institutes of Health (NIH), will be submitted for study by the scientific community.

"We are encouraged by this new data, which strengthens our confidence that Moderna's vaccine against Covid-19 should protect against these new variants detected," said boss Stéphane Bancel, quoted in the press release.

"But as a precaution, (...) we are testing a candidate (vaccine)" against the South African variant, "to determine if it would be more effective in increasing the levels (of antibodies) against that variant. and other potential future variants, ”he added.

"We believe it is imperative to remain proactive as the virus evolves."

- Third dose?

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A phase 1 study on this new formula, called mRNA-1273.351, will be launched in the United States.

It could be used to boost protection "in combination" with other vaccines, according to Moderna.

The company will also test the impact of injecting a third dose of its already existing vaccine.

The data concerning the reaction to the South African variant may be a source of "concern", responded Lawrence Young, a researcher at the University of Warwick, regretting a "vague" statement.

"A six-fold reduction in antibody titers can have consequences on the efficacy of the vaccine and (...) the duration" of protection, he said.

Monday's announcement is "good news," tweeted Akiko Iwasaki, a virologist at Yale University, on the contrary, saying he expected other laboratories to develop new formulas against the South African variant as well. .

The mutation observed in the variant that emerged in South Africa is of particular concern to scientists about its possibility of bypassing the immune protection conferred by vaccination.

Variants are different versions of the original coronavirus, which appear over time due to various mutations.

A normal phenomenon in the life of a virus.

Many mutations of Sars-CoV-2 have been observed since its appearance, the vast majority without consequence.

However, some may give it an advantage for its survival, including greater transmissibility.

BioNTech and Pfizer, the manufacturers of the main vaccine administered worldwide, have ensured that the latter was effective against the N501Y mutation, observed in particular on the British variant, and suspected of making it more contagious.

But their laboratory checks did not focus on the mutation (E484K) observed specifically on the South African variant.

© 2021 AFP