Long-Term Humoral Immune Response against SARS-CoV-2 after Natural Infection and Subsequent Vaccination According to WHO International Binding Antibody Units (BAU/mL) oleh Natalia Ruetalo, Bertram Flehmig, Michael Schindler, Lutz Pridzun, Angelika Haage, Marija Reichenbächer, Thomas Kirchner, Teresa Kirchner, Karin Klingel, Michael B. Ranke, Andrea Normann