How Omicron evades the immune system
The current wave of COVID-19 shows a particularly high risk of reinfection by the Omicron variant of SARS-CoV-2. What are the reasons for this? A team from the Centre for Emerging Viral Diseases at the University of Geneva (UNIGE) and the Geneva University Hospitals (HUG) analysed the neutralisation capacity of the antibodies of 120 people infected with the original strain of SARS-CoV-2 or one of its variants Alpha, Beta, Gamma, Delta, Zeta, or Omicron (sub-variant BA.1).
Unlike its predecessors, Omicron appears to be able to evade the antibodies generated by all the other variants. In vaccinated individuals, the neutralisation capacity is also lower, but remains much greater than natural immunity alone. This could explain why Omicron is responsible for a net increase in cases despite vaccination, but not in hospitalisations.
The research team took blood samples from 120 volunteers previously infected with one of the different variants, some unvaccinated and others vaccinated and infected before or after vaccination. "With an average age of between 28 and 52, no major comorbidities and having suffered from a mild to moderate form of COVID-19, this cohort represents the majority of cases in the population," explains Isabella Eckerle, head of the HUG-UNIGE Centre for Emerging Viral Diseases, who is also one of the investigators of studies conducted by the Population Epidemiology Unit.
"Omicron can evade existing immunity and cause infection, but hospitalisations and deaths due to COVID-19, even with Omicron, are still less frequent after vaccination. Nevertheless, SARS-CoV-2 retains an astonishing ability to mutate, which also appears to be accelerating. We need to remain vigilant, particularly as the epidemiological curves have been rising sharply since the appearance of BA.5, the most recent Omicron sub-variant", adds Isabella Eckerle.
This research was carried out with the support of the Swiss National Science Foundation (SNSF), the Fondation Ancrage bienfaisance of the Pictet Group and the Fondation privée des HUG.
A article was also published on this subject in the Tribune de Genève.
