COVID-19 Vaccination in Patients With Cancer and Patients Receiving HSCT or CAR-T Therapy: Immune Response, Real-World Effectiveness, and Implications for the Future

Patients with cancer demonstrate an increased vulnerability for infection and severe disease by SARS-CoV-2, the causative agent of COVID-19. Risk factors for severe COVID-19 include comorbidities, uncontrolled disease, and current line of treatment. Although COVID-19 vaccines have afforded some level of protection against infection and severe disease among patients with solid tumors and hematologic malignancies, decreased immunogenicity and real-world effectiveness have been observed among this population compared with healthy individuals. Characterizing and understanding the immune response to increasing doses or differing schedules of COVID-19 vaccines among patients with cancer is important to inform clinical and public health practices. In this article, we review SARS-CoV-2 susceptibility and immune responses to COVID-19 vaccination in patients with solid tumors, hematologic malignancies, and those receiving hematopoietic stem cell transplant or chimeric-antigen receptor T-cell therapy.