A recent Nature article reports that mRNA vaccines against SARS-CoV-2 confer improved survival among patients with advanced-stage non-small-cell lung cancer or melanoma receiving immune-checkpoint inhibitors owing to activation of systemic immunity, potentiating antitumour responses. This retrospective proof-of-principle study indicates the potential for combined therapeutic interventions, although both the timing of vaccination as well as the nature of the elicited immune responses requires further investigation.