In a case study, scientists of the German Center for Infection Research (DZIF) and the University Medical Center Hamburg-Eppendorf investigated the T-cell response of a cancer patient, who was suffering from prolonged COVID-19. No B cells were detectable in the patient’s peripheral blood, entailing that she had no possibility of forming anti-SARS-CoV-2 antibodies. SARS-CoV-2 virus particles were detectable in the patient for nearly three months after infection with the virus.