Nearly one in three people exposed to SARS-CoV2 is infected, and as many as two in five with the Omicron variant. In the case of immunity conferred by vaccination, infection or a combination of the two this rate drops to one in ten. However, immunity disappears within a few months, confirms a team from the University of Geneva (UNIGE) and Geneva University Hospitals (HUG), after revisiting epidemiological data collected in Geneva. While protection following infection appears to be slightly greater than after vaccination albeit at the risk of potentially severe symptoms vaccination reduces the contagiousness of patients over a longer period. As the number of cases rises again, air filtration, ventilation and the wearing of masks in the vicinity of vulnerable people appear to be necessary measures. These results can be discovered in the journal Nature Communications.