ABSTRACT
We investigated the association of SARS CoV-2 vaccination with COVID-19 severity in a longitudinal study of adult cancer patients with COVID-19. A total of 1610 patients who were within 14 days of an initial positive SARS CoV-2 test and had received recent anticancer treatment or had a history of stem cell transplant or CAR-T cell therapy were enrolled between May 21, 2020, and February 1, 2022. Patients were considered fully vaccinated if they were 2 weeks past their second dose of mRNA vaccine (BNT162b2 or mRNA-1273) or a single dose of adenovirus vector vaccine (Ad26.COV2.S) at the time of positive SARS CoV-2 test. We defined severe COVID-19 disease as hospitalization for COVID-19 or death within 30 days. Vaccinated patients were significantly less likely to develop severe disease compared with those who were unvaccinated (odds ratio = 0.44, 95% confidence interval = 0.28 to 0.72, P < .001). These results support COVID-19 vaccination among cancer patients receiving active immunosuppressive treatment.