Jude EB, Ling SF, Allcock R, et al. - Researchers investigated the association between vitamin D deficiency and risk of hospitalisation with COVID-19. Participants were people with results of serum 25-hydroxyvitamin D (25[OH]D) between April 1, 2020 and January 29, 2021. Patients were selected from two districts in the North West of England. Experts classified the last 25(OH)D level in the previous 12 months as ‘deficient’ if less than 25 nmol/L and ‘insufficient’ if 25-50 nmol/L. A higher risk of COVID-19 hospitalisation was observed in relation to vitamin D deficiency. This risk may be attenuated by widespread measurement of serum 25(OH)D and treating any unmasked insufficiency or deficiency via testing.