In a randomized placebo-controlled human BCG immunization study with subsequent yellow fever vaccine challenge, reduction of viremia was highly correlated with the upregulation of IL-1β, a cytokine associated with the induction of trained immunity, but not with the specific IFNγ response (Arts et al., 2018), supporting a key role for IL-1β as a mediator of trained immunity responses (Moorlag et al., 2018). Here, IL1B is linked to viral infectious disease.