Influenza vaccination in cancer patients receiving immune checkpoint inhibitors: A systematic review

Background: There is a concern that influenza vaccination may increase the incidence of immune-related adverse events in patients receiving immune checkpoint inhibitors (ICIs). The aim of this systematic review was to summarize the available data on the safety and efficacy of influenza vaccination in cancer patients receiving ICIs. Methods: Studies reporting safety and efficacy outcomes of influenza vaccination in cancer patients receiving ICIs were included. Only descriptive statistics were conducted to obtain a pooled rate of immune-related adverse events in vaccinated patients. Results: Ten studies assessing the safety and eight assessing the efficacy of influenza vaccination in cancer patients receiving ICIs were identified, for a total of 1124 and 986 vaccinated patients, respectively. Most patients had melanoma or lung cancer and received a single agent anti-PD-1, but also other tumour types and immunotherapy combinations were represented. No severe vaccination-related toxicities were reported. The pooled incidence of any grade immune checkpoint inhibitor–related adverse events was 28.9%. In the 6 studies specifying the incidence of grade 3-4 toxicities, the pooled incidence was 7.5%. No grade 5 toxicities were reported. No pooled descriptive analysis was conducted in studies reporting efficacy outcomes due to the heterogeneity of endpoints and data reporting. Nevertheless, among the eight studies included, seven reported positive efficacy outcomes of influenza vaccination. Conclusion: The results of this systematic review support the safety and efficacy of influenza vaccination in cancer patients receiving ICIs. These results are particularly relevant in the context of the SARS-CoV-2 pandemic.