In a study based on data from Israel's first two COVID waves, patients with vitamin D deficiency were 14 times more likely to have a severe or critical disease. The mortality rate among those with insufficient vitamin D levels was 25.6%, compared with 2.3% among those with adequate levels. These differences were consistent even after researchers controlled for age, gender, and history of chronic disease. Health officials in several countries have recommended vitamin D supplements during the pandemic.
Study: Vitamin D Deficiency Linked to Severe COVID (medscape.com)