> Early COVID-19 research found that most patients with optimum levels of vitamin D did not require ICU or breathing assistance and survived the infection.
Some sources point out that only 10-20% cases of covid are admitted to intensive care unit, and 80-90% of cases are mild.
I seriously doubt that up to 90% of the population has "optimum levels of vitamin D".
You can’t reverse an implication like that. “Most patients with X did not require Y” is not the same thing as “most patients who did not require Y had X”.
Some sources point out that only 10-20% cases of covid are admitted to intensive care unit, and 80-90% of cases are mild.
I seriously doubt that up to 90% of the population has "optimum levels of vitamin D".