Seroconversion rate after vaccination against COVID-19 in patients with cancer—a systematic review

Background: Coronavirus disease 2019 (COVID-19) has affected >210 million people worldwide. An optimal therapeutic approach for COVID-19 remains uncertain, to date. Since the history of cancer was linked to higher mortality rates due to COVID-19, the establishment of a safe and effective vaccine coverage is crucial in these patients. However, patients with cancer (PsC) were mostly excluded from vaccine candidates' clinical trials. This systematic review aims to investigate the current available evidence about the immunogenicity of COVID-19 vaccines in PsC. Patients and methods: All prospective studies that evaluated the safety and efficacy of vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were included, with immunogenicity after the first and the second dose as the primary endpoint, when available. Results: Vaccination against COVID-19 for PsC seems overall safe and immunogenic after well-conducted vaccination schedules. Yet the seroconversion rate remains lower, lagged or both compared to the general population. Patients with hematologic malignancies, especially those receiving B-cell-depleting agents in the past 12 months, are the most at risk of poor seroconversion. Conclusion: A tailored approach to vaccination may be proposed to PsC, especially on the basis of the type of malignancy and of the specific oncologic treatments received.