New virus variants of Sars-CoV-2 are constantly emerging. This is a natural process that occurs as the virus spreads: Every time the DNA of the virus is replicated, there is a chance of errors, so called mutations. On average, around two mutations of the SARS-CoV-2 virus occur every month.
These mutations permit scientists to distinguish between different genetic lineages or variants of the virus. While most mutations are of no use to the virus, in rare cases they may prove advantageous. For instance, some variants may be more transmissible. However, the manner in which they infect human cells remains the same.
At the moment, the most widespread virus variants are different subvariants of Omicron (e.g. XBB.1.5 and EG.5.1). These subvariants have different changes in their genetic material, some of which occur in the spike protein region.
The from Moderna and Pfizer/Biontech as well as the from Johnson & Johnson offer also with the Omicron variant a high level of protection against a severe course of the disease. In contrast, they provide only limited protection against infection with Omicron (asymptomatic or mild course). The of the different vaccines towards the new variants is currently being further investigated.
The and can be modified relatively quickly and easily, if necessary, to take account of any new virus variants. from Moderna and from Pfizer/Biontech are authorized as booster vaccines in Switzerland. In studies, these adapted vaccines achieved a stronger immune response against the Omicron variant than the original vaccines. It is not yet fully clear whether the adapted vaccines also provide better protection against infection and a severe course of disease caused by Omicron