Europe is currently facing a new wave of COVID-19, one of the explanations being that the new viral variants avoid the immune barriers posed by the vaccine or a previous infection.
Coronavirus FrancePhoto: Gao Jing / Xinhua News / Profimedia
An increase in the number of cases on the continent was registered in almost all European countries amid relaxations, but also a decrease in immunity among the population. .
It is now known that the protection offered by vaccines and previous infections decreases after a few months.
“People who contracted Omicron BA.1 infection in December are now less protected than they were earlier this year,” Samuel Alizon, director of research at CNRS (National Center for Scientific Research in France), told AFP. ).
“The same goes for the immunity offered by vaccines: although they remain very robust against severe forms of the disease, their protection decreases slightly against less severe infections,” the French specialist added.
“Ambush” of the sub-variants BA.4 and BA.5
But this new wave is also explained, according to scientists, by the spread of two new subvariants of Omicron – BA.4 and, especially, BA.5.
In France, according to the latest bulletin published by Santé Publique France, a gradual replacement of the BA.2 subvariant has been observed for several weeks, with the multiplication of infections caused by the BA.5 (41%) and BA.4 (6) subvariant %) in the week of June 13-19.
These subvariant spreads all the faster as they appear to benefit from a double advantage of contagiousness and an immune “escape”, ie they have a great capacity to avoid the immune response.
The same was true for the Omicron BA.1 subvariant, which was much more capable than Delta of infecting vaccinated or already infected people.
Going through the disease might mean nothing
Researchers have long believed that going through the disease takes the place of protection, at least for a certain period of time.
But with the spread of Omicron subvariants, it seems that going through the disease means almost nothing (in terms of the risk of reinfection – no), said the authors of a study conducted by Imperial College London and published in mid-June in the journal Science.
The scientists analyzed blood samples taken from more than 700 medical staff in the United Kingdom. All had received three doses of COVID-19 vaccines and were infected with the original strain of SARS-CoV-2 virus or variants thereof.
Their results highlighted that people who had been infected with Omicron in the past had a good immune response against the original coronavirus strain and its early variants, but a poor reaction against the Omicron variant itself.
For a time, it was thought that Omicron infection could be “almost beneficial, a kind of natural booster,” said Rosemary Boyton, co-author of the British study. “However, I found that infection weakens the immunity against Omicron or not at all in some cases. This phenomenon, together with the decline in immunity a few months after vaccination, may explain the massive increase we are seeing in new cases of infection, with many people being re-infected at short intervals, “she added.
“We are talking about a real complexity of the Omicron variant”
“We are facing highly contagious variants, which act as a kind of secret agents that pass under the radars of the immune system; we are talking about a real complexity of the Omicron variant “, declared last week Gilles Pialoux, head of department at the Tenon Hospital in Paris.
These “highly contagious” variants require an increase in the level of protection for the most vulnerable, “the French doctor added.
However – and this is good news – vaccines remain effective against severe forms of COVID-19 disease.
For most European countries, the top priority is for the elderly and immunocompromised to receive the second booster dose (second booster).
“Currently, the level of immunity among the population is good, but not perfect,” Alain Fischer, chairman of the French Vaccination Strategy Guidance Council, said on Sunday.
“That is why we must recommend the second booster for people over 60 and for frail people, whose immune systems and memories are less robust,” added the French specialist.
Increased infections in Israel as well
And Israel is facing an increase in the number of infections.
Dr. Nadav Sorek, director of the Infectious Diseases Laboratory at Samson Assuta Ashdod Hospital, said Monday that 25% of coronavirus antigen tests were now positive, up from 10% last month.
“The significance is twofold and worrying in light of the growing number of tests,” he said.
“If the criterion for being in another wave of COVID is an extreme increase in the number of positive tests, then we are in the middle of a wave. In recent weeks, we have seen an increase in positive tests in the total number of tests for corona detection and identification, and if we take into account that the number of tests has increased at the same time, then the reality is even more complex, “he said.
Israeli as well as French authorities have recommended wearing a mask in enclosed spaces. (Sources: AFP, Agerpres, Jerusalem Post)