Patients with cancer are considered vulnerable to severe acute respiratory syndrome coronavirus 2 infection and have been prioritized in the vaccination process in several countries, including Taiwan. In addition, international oncological societies favored COVID-19 vaccination for cancer patients on the basis of risk and benefits evaluation of all available data. However, patients with cancer were excluded from severe acute respiratory syndrome coronavirus 2 vaccines registrational trials and the investigators lack data regarding the safety and efficacy of vaccination in this population. Under this perspective, the investigators undertook a large prospective study enrolling patients with solid cancers, hematologic malignancies as well as healthy volunteers for the kinetics of anti-severe acute respiratory syndrome coronavirus 2 antibodies after COVID-19 vaccination on different anticancer therapy. Major inclusion criteria for this cohort of the study included: (1) age above 20 years; (2) presence of solid organ malignancies treated with immunotherapy, chemotherapy, Targeted therapy irrespective of the treatment phase; and (3) eligibility for vaccination.