A new study published in the journal Cell raises the possibility that some of us are already immune to Covid-19. An interesting hypothesis, but not unanimous.
Several researchers argue that the coronavirus crisis is now behind us, or about to be, thanks to the principle of cross-immunity . If their hypothesis is far from being shared by all, certain elements still lead us to consider the idea. But what exactly are we talking about?
As part of recent work carried out at the Center for Infectious Desease and Vaccine Research, researchers from the University of San Diego (USA) examined blood samples from 20 patients who had been exposed to Covid-19, but who had not been infected.These patients had therefore developed an immune response to the disease.
The researchers then isolated immune cells from the blood of these patients – CD4+ and CD8+ T cells – capable of recognizing several SARS-CoV-2 proteins (proteins of spikes, M, N proteins, among others).
These same researchers also examined blood samples taken between 2015 and 2018 from 20 healthy US donors. It was found that about half of the samples analyzed contained CD4 + cells reactive against SARS-CoV-2 proteins.
Since these donors could not have been exposed to Covid-19 at that time, where did this immune response come from?
What this study proposes today is that these patients – and more broadly, part of the population – could have developed antibodies to fight the SARS coronavirus. -CoV-2 by having contracted mild viral illnesses in the past. This is called cross-immunity:immunity acquired during a first infection, capable of protecting, later, against another genetically close infectious agent.
Still according to these researchers, between 40% and 60% of the population could thus today be immunized against Covid-19. If this (unverified) hypothesis is seriously considered, given the virulence of the pathogen since its declaration and the number of people affected, Sars-CoV-2 would no longer have many people to infect. We could then imagine that the virus is currently on the decline , and that there will be no second wave as devastating as the first.
This analysis is shared by epidemiologist Laurent Toubiana, director general of the Research Institute for the Valorization of Health Data (IRSAN):“ A significant part of the population may not be susceptible to the coronavirus . The epidemic wave has passed and it has infected everyone, but it will not come back because all the people who should have been affected have already been affected. The epidemic is therefore coming to an end “, he said on France Inter.
“This virus is not a marathon runner, it is a sprinter:it wears out very quickly sums up Professor Jean-François Toussaint, director of the Institute for Biomedical Research and Sports Epidemiology (IRMES).
Several indicators seem to point in the same direction. The daily number of intensive care admissions has indeed been decreasing since April 8. The same goes for the number of daily deaths. These trends could nevertheless have more to do with the containment measures adopted several weeks ago, which now seem to be bearing fruit. It is therefore important, in the current state of things, not to declare victory yet.
“All we can say is that today, we have no warning signal. But it is too early to conclude from this observation that everything will be fine “, told AFP epidemiologist Daniel Lévy-Bruhl, head of the respiratory infections unit within Public Health France. “The Sword of Damocles of a “recovery of the epidemic dynamics is, according to him, still present . He thus considers "premature to base hope on cross-immunity “, a hypothesis “far from being unanimous and far from being confirmed .
Source
