evidence: Severe hyperinflammatory response occurs in a fraction of patients with COVID-19.7 Similarly, COVID-19 vaccines have the potential to evoke intense immunologic responses.8 Here, we describe a case of an anticancer response after COVID-19 vaccination. Histology analysis and tumor molecular profiling suggested that the primary tumor was poorly immunogenic, which is associated with poor responses to the most commonly used cancer immunotherapy. Notably, the patient reported grade 3 systemic adverse events after the second dose of the COVID-19 vaccine, which was preceded by spontaneous tumor regression, indicating that an intense inflammatory host response stimulated by the vaccine may have promoted an antitumor response. [...] In summary, this patient’s clinical course and the analysis of prevaccination and postvaccination tumor samples support the hypothesis that stimulation of the innate immune system by the mRNA-1273 COVID-19 vaccine induced systemic immune activation and led to a robust and persistent anticancer response, represented by radiological tumor shrinkage and an ‘anticancer’ TIME composition. To our knowledge, this is the first reported case of COVID-19 vaccine-induced tumor regression and the first report of spontaneous tumor regression in a patient with salivary myoepithelial carcinoma. Host and tumor characteristics that led to this phenomenon remain unclear.