Immune Checkpoint Inhibitors and Vaccination: Assessing Safety, Efficacy, and Synergistic Potential

Although immune checkpoint inhibitors (ICIs) have become predominant therapies for cancer, the safety and efficacy of combining ICIs with vaccinations remain areas of needed investigation. As ICIs gain broader clinical application, the relevance of current vaccination guidelines for cancer patients-largely developed in the context of cytotoxic therapies-becomes increasingly uncertain. Although data support the safety of combining inactivated influenza and mRNA SARS-CoV-2 vaccines with ICI therapy, comprehensive data on other infectious disease vaccines remain scarce. Notably, the combination of ICIs with infectious disease vaccines does not appear to exacerbate immune-related adverse events, despite the heightened cytokine activity observed. However, the efficacy of vaccines administered alongside ICIs in preventing infectious diseases remains poorly supported by robust evidence. Preliminary findings suggest a potential survival benefit in cancer patients receiving ICI therapy alongside influenza or SARS-CoV-2 vaccination, though the quality of evidence is currently low. Moreover, the synergistic potential of combining therapeutic cancer vaccines, particularly mRNA-based vaccines, with ICIs indicates promise but with a paucity of phase III data to confirm efficacy. This review critically examines the safety and efficacy of combining ICIs with both infectious disease vaccines and therapeutic cancer vaccines. While vaccination appears safe in patients undergoing ICI therapy, the impact on infectious disease prevention and cancer treatment outcomes warrants further rigorous investigation.