SARS-CoV-2 antibody development and immunity will be crucial for the further course of the pandemic. Until now, it has been assumed that patients who were infected with SARS-CoV-2 develop antibodies as it is the case with other coronaviruses, like MERS-CoV and SARS-CoV. In the present study, we analyzed the antibody development of 77 oncology patients 26 days after positive RT-qPCR testing for SARS-CoV-2. RT-qPCR and anti-SARS-CoV2-antibody methods from BGI (MGIEasy Magnetic Beads Virus DNA/RNA Extraction Kit) and Roche (Elecsys Anti-SARS-CoV-2 immunoassay) were used, respectively, according to the manufacturers’ specifications.Surprisingly, in only 6 of 77 individuals with a confirmed history of COVID-19 antibody development was detected. Despite of multiple testing, the remaining patients did not show measurable antibody concentrations in subsequent tests. These results undermine the previous hypothesis that SARS-CoV-2 infections are regularly associated with antibody development and cast doubt on the provided immunity to COVID-19. Understanding the adaptive and humoral response to SARS-CoV-2 will play a key-roll in vaccine development and gaining further knowledge on the pathogenesis.