Cancer Patients and the COVID-19 Vaccines: Considerations and Challenges

Simple Summary Coronavirus disease 2019 (COVID-19) is the greatest present-day public and global health challenge, and patients with cancer are especially vulnerable, emphasizing the importance of vaccination. However, little is known about the effects of cancer and treatment on vaccine effectiveness and its safety. The aim of this review is to explore current literature regarding the immune response rate and safety profile of COVID-19 vaccination in patients with solid and hematologic cancers and those receiving various forms of treatment. Immune response rates were described to be lower amongst cancer patients, especially those with hematologic cancers, and those receiving chemotherapy, radiotherapy, or immunosuppressants. Nevertheless, sufficient immune response was still generated in many patients, and vaccination was overall described to be safe and well-tolerated, therefore supporting vaccine encouragement. Few guidelines exist for COVID-19 vaccination amongst cancer patients, fostering uncertainty regarding the immunogenicity, safety, and effects of cancer therapies on vaccination, which this review aims to address. A literature review was conducted to include the latest articles covering the immunogenicity and safety of COVID-19 vaccination in patients with solid and hematologic cancers receiving various treatments. Lower seropositivity following vaccination was associated with malignancy (compared to the general population), and hematologic malignancy (compared to solid cancers). Patients receiving active cancer therapy (unspecified), chemotherapy, radiotherapy, and immunosuppressants generally demonstrated lower seropositivity compared to healthy controls; though checkpoint inhibition, endocrine therapy, and cyclin dependent kinase inhibition did not appear to affect seropositivity. Vaccination appeared safe and well-tolerated in patients with current or past cancer and those undergoing treatment. Adverse events were comparable to the general population, but inflammatory lymphadenopathy following vaccination was commonly reported and may be mistaken for malignant etiology. Additionally, radiation recall phenomenon was sporadically reported in patients who had received radiotherapy. Overall, while seropositivity rates were decreased, cancer patients showed capacity to generate safe and effective immune responses to COVID-19 vaccination, thus vaccination should be encouraged and hesitancy should be addressed in this population.