Since the start of the pandemic, the phenomenon of reinfection with Covid-19 has been observed several times. But in recent weeks, especially because of the Omicron variant, it has amplified. La Dépêche explains this phenomenon and its consequences.
“First contamination in October 2020 before the vaccines, second at Christmas 2021, this time, with the Omicron variant.” “Positive test in October 2020, December 2021 and January 2022!” “I was contaminated in the first wave by my student daughter and contaminated again by Omicron via my husband this time.” The testimonies of double, triple or even quadruple Covid-19 infections have multiplied in recent weeks. It is no longer so rare to find people around you who claim to be positive for the second times since the 5th wave swept through France.
With Omicron, reinfection 5.4 times higher than with Delta
A study carried out in Israel and published by the Kan public broadcaster, argues that one in nine cases of Covid-19 in the Jewish state diagnosed would be a reinfection. And, according to this same report, a large part of these reinfected people would have received, beforehand, one or more doses of vaccine.
If this phenomenon is not new, it seems to have exploded in recent weeks. Very contagious, “the Omicron variant can spread to people who have had two doses of vaccine or who have been previously infected”, wrote, at the end of December, the Institut Pasteur. An observation confirmed by scientists from Imperial College London. In a report released last month, they write, in fact, that reinfection with this variant would be 5.4 times greater than Delta. They go even further and claim: “The study demonstrates the extent to which Omicron evades the immunity conferred by infection or complete vaccination”, they note.
Limited severe forms
“The virus, like many RNA viruses, is constantly evolving, explains Jacques Izopet, head of the virology department at the Toulouse University Hospital. These different variants have the property of stimulating the immune system and therefore of inducing antibodies and other protective elements, such as lymphocytes. But the virus, as it evolves, will sometimes tend to escape these means of defense and this is what we are witnessing today with the Omicron virus.
JACQUES IZOPET
According to this expert, this new variant has, in its genome, about thirty mutations which cause its surface protein – the one recognized by antibodies – to be modified. “As a result, continues the Toulouse virologist, when a person has been vaccinated or who has had an infection with a previous coronavirus, they can catch another variant, but thanks to the cellular immunity generated by vaccination or previous infections , it has protection against the most serious forms.”
But what about the collective immunity hoped for, even promised, by certain health professionals in the coming weeks due to the extreme contagiousness of Omicron? Doesn’t the possibility of being multi-contaminated undermine this theory that the population is immunized thanks to vaccination and/or a previous infection? “No, replies Jacques Izopet. The fact that a large number of people are in contact with the Omicron virus, reinforces the level of immunization and therefore of protection of the general population.”
For this specialist, vaccination remains the best bulwark against infection, even if it is struggling, for the moment, to adapt to the incessant mutations of the virus. But nothing says that by the time a 100% effective vaccine against Omicron comes to market, other mutant variants have not appeared on the world stage.