In France, the so-called English variant now represents two thirds of contaminations.
Appeared at the end of last September in south-east London, it quickly proved to be much more transmissible to the point of becoming the majority in just a few weeks across the Channel, as in France.
Experts were until now reserved on its greatest danger.
The studies were contradictory.
A large-scale assessment, published on March 10 in the British Medical Journal, leads to worrying conclusions: "There is a high probability that mortality is increased during infection with the English variant", write the authors, researchers at the University of Exceter and Bristol.
Their work is based on solid data.
The experts looked at 54,906 people who tested positive in town for the English variant.
They were compared with as many positive patients but with the strain virus, during the same period, between October 1, 2020 and January 29, 2021. The patients of the two groups had the same characteristics, age, sex, social background.
Within 28 days of the test, 227 deaths were observed among the 54,906 patients infected with the English variant.
In the other group, identical to the numerical plan, 141 deaths were to be deplored.
The death rate drops from 2.5 per 1000 with the initial virus to 4.1 per 1000 with the English variant.
The mortality rate would therefore be on average 64% higher.
According to the authors, if the risk of mortality is increased, it remains quite low.
More contagious
"It is a very well done, high quality study, which gives very precise data," comments Professor Élisabeth Bouvet, president of the technical committee on vaccinations of the High Authority for Health.
However, it does not give any explanation to understand why this mortality is higher.
Moreover, other studies have shown that the greater contagiousness of this English mutant was due to its greater ease of binding with the cells of the organism.
"Viruses with mutations that we see appear constantly adapt to survive better," says Pr Bouvet.
So far, the English variants have been studied more than the South African and Brazilian variants.
The efficacy of vaccines on these mutated strains is the subject of much speculation.
“For now, the vaccines used in France, Pfizer, Moderna and AstraZeneca, should keep their effectiveness against the English variant, notes the virologist.
Data regarding their impact against the South African variant is more mixed.
It is only in real time and on a large scale that it will be possible to determine whether vaccination campaigns are successful in controlling these viruses.
"