Just look at that! Suddenly even vitamin D is in the news:
https://www.timesofisrael.com/israeli-study-offers-strongest-proof-yet-of-vitamin-ds-power-to-fight-covid/
Patients with vitamin D deficiency were 14 times more likely to have severe or critical Covid: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0263069