Since late 2019, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has spread globally, becoming one of the largest known pandemics. Vaccination against the virus is one of the most important tools in combating the pandemic. However, not all vacci­nated people develop robust and protective antibody titres and thus, also depending on the vaccine used or the specific endpoint in the study, protection rates between 50 % and 95 % have been reported.

In principle, the reaction of the immune system to a vaccination can be a cellular and a humoral response. In the case of the humoral response, it is primarily the antibodies formed that provide evidence of a corresponding reaction and possibly protection. Of particular interest are antibodies to the Receptor Binding Domain (RBD) of the virus since they correlate with the neutralising antibody titre and are thus decisively responsible for protection. The neutralising antibodies prevent the binding of the virus to the specific cell receptor and thus the penetration of the virus into the host cell.