In single-SNP MR analyses, genetically predicted higher OAS1 was associated with lower risk of severe COVID-19 vs. population (OR [95% CI] per SD genetically predicted OAS1 concentrations: 0.52 [0.42, 0.65], p=5 × 10–9), hospitalised COVID-19 vs. population (0.63 [0.53, 0.75], p=1 × 10–7) and susceptibility to COVID-19 vs. population (0.79 [0.71, 0.87], p=2 × 10–6). The gene discussed is OAS1; the disease is COVID-19.