Impact of COVID-19 vaccination on cancer patients: safety, efficacy, and long-term effects.

Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), led to a worldwide pandemic in 2020. Cancer patients represent a highly vulnerable group for COVID-19 infection and are associated with poor outcomes due to their immunosuppressive status, owing to malignancy itself or anticancer therapies. Several approved COVID-19 vaccines were assessed for their effectiveness in the general population. However, initially, cancer patients were excluded from large landmark trials, leading to a paucity of data. This article presents a narrative review that synthesizes findings from peer-reviewed clinical trials, real-world cohort studies, and expert guidelines to assess the current evidence. This review assesses the safety, efficacy, and long-term effectiveness of COVID-19 vaccination in patients with cancer. Accumulated evidence from multiple clinical trials and real-world data suggests that COVID-19 vaccines are generally well-tolerated, safe, and efficacious in patients with both solid and hematologic types of cancer, eliciting moderate adverse reactions and rare severe reactions, including immune-related adverse events, thrombotic events, and anaphylaxis. Vaccine-induced humoral response and cellular response are often weakened in cancer patients, especially those with hematologic malignancies, compared to those of non-cancerous individuals. However, the immunogenicity in cancer patients improves significantly with booster doses. Further, seroresponse against SARS-CoV-2 variants increases with additional booster doses, signifying the importance of personalized booster approaches. Despite this, vaccinated cancer patients develop breakthrough infections, which are associated with hospitalization and higher mortality compared to the general population. Moreover, long-term follow-up of vaccinated cancer patients suggests that they demonstrate durable immune responses, with rare reports of cancer recurrence or remission that require further evaluation. Collectively, COVID-19 vaccination is a practical and valuable approach for alleviating risk and improving outcomes in patients with cancer.