Deconvolving SARS-CoV-2 mRNA vaccine impact on immunotherapy-related survival

Real-world data suggest that SARS-CoV-2 mRNA vaccines, administered within 100 days of immune checkpoint inhibitor (ICI) treatment ("peri-ICI vaccination"), may improve ICI effectiveness through synergistic immune priming. In an independent real-world cohort and re-analysis of a published cohort, both from tertiary cancer centers in the USA, multiple analyses did not support a treatment-synergy hypothesis. Applying a prior analytic framework, although longer survival with peri-ICI vaccination was observed at the start of the pandemic, this association was not seen in periods when vaccination was broadly available. Longer survival with vaccination in the early pandemic was also not specific to ICI therapies. Progression-free survival during periods of high vaccine uptake was not longer than in pre-vaccination periods. Together, these findings indicate that the previously reported vaccination survival advantage is largely explained by selection bias, with patients who had more favorable prognoses more likely to receive SARS-CoV-2 vaccination, particularly in the early pandemic.