Sjögren’s syndrome is an autoimmune disease characterised by lymphocytic infiltration of exocrine glands, but also systemic features such as arthritis, vasculitis, pulmonary and neurological dysfunction. Despite its impact on quality of life and physical function, no disease-modifying drugs have been approved. Some observational studies have linked vitamin D deficiency to increased Sjögren’s risk [1], but these findings are susceptible to confounding and reverse causation. Clinical trial evidence suggests that vitamin D supplementation reduces overall autoimmune disease risk [2], but whether this applies to Sjögren’s is not known. Mendelian randomization (MR) uses genetic variants as instrumental variables to estimate the effect of an exposure on an outcome that is typically more robust to these biases. Prior MR studies found no evidence for a link between vitamin D and Sjögren’s, but were limited by poor case definition and/or statistical power [3,4]. The aim of this MR study was to estimate the effect of genetically predicted vitamin D level on risk of primary Sjögren’s syndrome.