Immunity for the Covid-19, a topic that has animated the debates of experts over several months. Three media publish date versions in opposition, which will not further confusion among the French.
While a blog of the World relays to a study published in the journal Nature explaining that ” half the population possess an immunity Covid-19 pre-existing “. For its part, the reader of le Figaro Sciences will walk away with the feeling ” that there is no cross immunity to the Covid 19 “.
What is cross-immunity ?
The article in Nature (*) we can conclude that cross-immunity is also connected to the memory cell of the lymphocytes T. This is a good thing, because the assumption of immunity against the Covid-19 was based primarily on the production of antibodies. The study is interested in the recognition of the NP protein of the virus Covid-19 (SARS-Cov2) by t lymphocytes. This cellular response was found in 36 patients convalescents of the Covid-19, but also in 23 patients who were infected by the SARS-Cov1 2003, which would imply a memory cell of the lymphocytes T in the long term. For the reader who is not warned, does this mean that there would be a cross-reactive immunity 17 years after.
Very surprising, this cellular response is specific to the Covid-19 was also detected in 37 individuals who had no history of contamination or contact neither with the SARS-Cov1 or with the SARS-Cov2.
Is this assertion could have an impact on the conclusions of some studies ?
Cross-immunity, if proven, would explain a lot of things in the pandemic of sars Coronavirus in which we live, including in the result of some studies because of the inclusion and randomization of patients, they are not all equal in front of the disease and therefore do not have the same reaction to the virus. A possible explanation for the relative failure of the various therapies tested since we would have randomized the patients so that they did not need and that they probably did not have the same capacity for cellular immune. This phenomenon has probably been accentuated by the stage of the disease presented by the patient at the time of its inclusion in the test, not to mention his pre-existing medical conditions (comorbidities).
Of mutations in the virus could also explain the differences in virulence and infectiousness observed, to this day, all over the world. This would suggest that there are several strains of the virus that are currently circulating. A virus is mutating, it can get worse (more virulent and contagious) or, on the contrary, less.
(*) Article in Nature in English