A very limited number of intervention trials, most including less than 30 patients, have been published. The only phase III study, our VITdAL-ICU study recruited from 2010 to 2012 and (n=475) did not find a difference in the primary endpoint "length of hospital stay" between placebo and high-dose vitamin D3. However, there was a non-significant absolute risk reduction in all-cause hospital mortality in the total population. The difference was larger (17.5%) and significant in the predefined subgroup of patients with severe vitamin D deficiency at baseline, see Kaplan Meier curve below (n=200, 28.6 vs 46.1%, p=0.01, 0.56 (0.35-0.90) ), corresponding to a number needed to treat of 6. (51) As this was only a secondary endpoint in the predefined subgroup with severe vitamin D deficiency, this finding is hypothesis generating and requires further study, leading to this application.