Radujkovic, et al. “Vitamin D Deficiency and Outcome of COVID-19 Patients.” Nutrients 2020, 12(9), 2757; https://doi.org/10.3390/nu12092757
The study found: “VitD deficiency was associated with higher risk of IMV/D and death (HR 6.12, 95% CI 2.79–13.42, p < 0.001 and HR 14.73, 95% CI 4.16–52.19, p < 0.001, respectively)."
Vitamin D deficiency in Covid-19 patients, both those in hospital and those sick at home, resulted in an increased risk that the patient would either end up on mechanical ventilation or end up dead, or both (most likely both). The increase in risk for needing ventilation and/or dying was 6.12 times, and the increased risk in death was 14.73 times.
The study authors state: “VitD-deficient patients had a higher hospitalization rate and required more (intensive) oxygen therapy and IMV. In our patients, when adjusted for age, gender, and comorbidities, VitD deficiency was associated with a 6-fold higher hazard of severe course of disease and a ~15-fold higher risk of death.”
Those with normal levels of vitamin D in the blood had a much lower risk of having a severe case of Covid-19.
Do you want to be certain your vitamin D levels are high enough? Yes, you do. This is the 22nd study of this type, showing risk reduction for vitamin D versus Covid-19. You want that risk reduction. To be certain your levels of vitamin D are high enough, take 50,000 IU per day for a month, then reduce to 50,000 IU once a week (or 5000 IU per day or 10,000 IU every other day).
You want a blood level of at least 40 ng/ml (which is at least 100 nmol/liter). You could go to your doctor, get a blood test, find out the exact level, then take the supplement, then go to your doctor again in a month or two. Or just take the supplement. It's safe. Just take it. There's a deadly pandemic ripping through humanity, and we're about to hit one million dead worldwide.
If you are not taking vitamin D, you must be either a fisherman or a lifeguard or an idiot. If everyone on the planet raised their vitamin D levels by sunshine or supplements, the pandemic would be reduced in severity so much so that it would no longer be a pandemic. There would only be isolated pockets of the disease, where the population was too stupid to get out in the sun or take an inexpensive vitamin supplement.