The way in which the Covid-19 epidemic will evolve in the coming weeks, especially since the emergence of more contagious variants, is, and rightly so, a major concern of the population, doctors, and authorities. This issue does not prevent us from also wondering about a more distant future. Will we one day be rid of SARS-CoV-2? Or will we have to live with it? And in the latter case, with what type of risk for the population? Rustom Antia, of Emory University in Atlanta, and his colleagues tried to respond. According to their models, it is likely that the infection with the new coronavirus will one day look like a simple cold.
To achieve this scenario, the team looked at the epidemiological parameters of SARS-CoV-2 and six other coronaviruses known to have humans as a host: four benign (229E, NL63, OC43 and HKU1) because they only cause colds, and two others (le SARS-CoV and MERS-CoV), responsible for limited lung disease pandemics in 2002 and 2012. A central hypothesis of the study is that these coronaviruses trigger similar immune responses. Difficult to believe in view of the current Covid-19 record, but this is explained by the fact that the new coronavirus affects a “naive” population, that is to say individuals whose immune system has failed. never been confronted with the infectious agent, and therefore more vulnerable.
Three parameters (IES, IEP et IEI) were selected to define the protection offered by immunity (IE for “immune efficacy”) against a coronavirus. This is because immunity can prevent the pathogen from replicating and therefore prohibit any reinfection (IES), or “only” to attenuate the disease in the event of reinfection (IRP) or even reduce transmissibility (IEI). In the same individual, these three parameters, which depend on different players in the immune system, decrease over time, but with their own rhythms, for example depending on the frequency of reinfections.
An analysis of the available data concerning antibodies against benign coronaviruses in children and adults made it possible to measure the dynamics of these parameters. These data reveal in particular that the immunity blocking infection (IES) decreases rapidly, while disease-reducing immunities (IEP et IEI) are long lasting. Another result, the primary infection with one of the four benign coronaviruses occurs between 3.4 and 5.1 years. At 15, everyone was infected.
Thanks to this information, the authors show that the dangerousness of the virus will diminish without however disappearing, following in this the evolution of the four benign coronaviruses (SARS-CoV and MERS-CoV are not concerned, because they do not have not spread enough). As a reminder, OC43 is suspected of having killed 1 million people during a pandemic in 1890. The key element of this scenario is the fact that the infection is not serious in children : in the future, in endemic conditions, only children, the vast majority of whom only develop mild forms, would then be affected by SARS-CoV-2; older, they would remain protected and would always be more so with each reinfection.
Without a vaccine, this situation would arise – at the cost of numerous deaths and severe forms -, within a few years to a few decades depending on the speed of spread of the coronavirus (and possible new variants) and the duration of the immune response. developed against him, the latter data being still poorly known given the recent appearance of the virus. Vaccines (only for adults) would reduce this time to a year or even six months. The authors warn their conclusions would all be different with a pathogen causing serious illness in young people. Since this is not the case, that the parents prepare to say without shuddering to their offspring: “Put on your scarf, otherwise you will catch Covid-19 …” To your wishes!