Study centers are at the locations of the six Bavarian university hospitals (University Hospital Augsburg, University Hospital Erlangen, University Hospital Munich, Klinikum Rechts der Isar of the Technical University of Munich, University Hospital Regensburg, University Hospital Würzburg).

The primary recruitment route is via the cases reported to the participating health authorities in Bavaria with an initial SARS-CoV-2 detection. One group includes people infected with SARSCoV-2 after at least one COVID-19 vaccination (breakthrough infections). A second control group consists of SARS-CoV-2 infected people without previous COVID-19 vaccination. The subjects are repeatedly visited by the study staff during the acute disease phase of approximately 3 – 4 weeks in order to document the clinical course and to obtain respiratory and blood samples and for a final visit after 4 – 5 months.

The level of virus concentration and the duration of virus excretion are measured in the respiratory samples. Determining the virus load in the course of the disease also allows a statement to be made about the kinetics of virus replication and the infectivity of the individual. The humoral and cellular immune responses on the clinical, immunological and virological course of a SARS-CoV-2 infection are examined in the blood samples.

Based on this data, risk factors and possible causes for insufficient protection should be identified (primary or secondary vaccination failure) after a COVID-19 vaccination. It can also be examined whether a previous COVID-19 vaccination influences the course of a SARS-CoV-2 infection. In particular, it should be checked whether a previous vaccination leads to an easier course of the disease or causes a different form of the COVID-19 symptoms and complications.