Clinical centers including MD Anderson reported retrospective analyses suggesting patients who received an mRNA COVID‑19 vaccine within roughly 100 days of starting checkpoint inhibitors lived longer than unvaccinated counterparts. Presentations at ESMO and related publications described survival differences and hypothesized vaccine‑driven immune activation as a mechanism. Researchers cautioned the analyses are retrospective and subject to confounding; investigators from MD Anderson and collaborators called for prospective studies to test causality and timing. The findings nonetheless prompted interest in immunologic interactions between prophylactic vaccines and cancer immunotherapy.