(Preprint) (meta analysis)
COVID-19 mortality risk correlates inversely with vitamin D3 status, and a mortality rate close to zero could theoretically be achieved at 50 ng/ml 25(OH)D3: Results of a systematic review and meta-analysis
Meta analysis of 8 studies with vitamin D levels measured pre-infection or on the day of hospital admission, showing a correlation between the levels and mortality. Authors recommend combining vaccination with vitamin D supplementation to maintain levels above 50 ng/ml. Authors extrapolate to predict a point of zero mortality, however there is no reason to predict a linear relationship where zero mortality would be reached.
Borsche et al., 9/25/2021, preprint, 3 authors.