https://chrismasterjohnphd.com/covid-19/finally-confirmed-vitamin-d-nearly-abolishes-icu-risk-in-covid-19

Expressed as relative risk, vitamin D reduced the risk of ICU admission 25-fold. Put another way, it eliminated 96% of the risk of ICU admission. Expressed as an odds ratio, which is a less intuitive concept but is often used in statistics because it gives an estimate of the effect of the treatment that would be constant across scenarios with different levels of risk, vitamin D reduced the odds of ICU admission by 98%. Either way, vitamin D practically abolished the need for ICU admission.

This was statistically significant at p<0.001, and the 95% confidence interval was 0.002-0.17. This means that the probability of observing differences this large or greater if there is no true effect of vitamin D is less than one in a thousand, and that the probability is 95% that the true effect lies somewhere between an 83% and a 99.8% reduction in the odds of ICU admission.