evidence: A recent study has shown a correlation between vitamin D deficiency and COVID-19 severity and mortality. The study is based on data from Israel’s first two coronavirus waves before vaccines were widely available. It found that people with a vitamin D deficiency are more likely to develop a severe or critical case of COVID-19 compared to people who had sufficient levels of the vitamin in their blood. Patients with a vitamin D deficiency were 14 times more likely to have a severe or critical case of COVID-19. Additionally, the mortality rate for those with insufficient vitamin D levels was 25.6%, compared with 2.3% among those with adequate levels.