The Role of Vitamin D in COVID-19 Survival and Prevention: A Meta-analysis

Background: COVID-19 is still ongoing with frequently discovered new strains, although vaccines are highly effective for prevention. Literature on vitamin D supplementation in COVID-19 prevention and its effect on survival is scarce. This meta-analysis assessed the role of vitamin D supplementation in COVID-19 prevention and survival.
Methods: Four databases (Web of Science, SCOPUS, PubMed, MEDLINE, and the first 100 articles of Google Scholar) were searched for articles published up to September 2023. The keywords used were COVID-19, mortality, vitamin D supplementation, calcitriol, cholecalciferol, Calcifediol, survival, death, and prevention. Six hundred and seven studies were retrieved, and four hundred and three remained after duplication removal; of them eighty-three full texts were screened, and of them, only sixteen (prospective, randomized controlled trials, and retrospective studies) were included in the final meta-analysis.
Results: Sixteen observational studies including 5905,109 patients and 186,500 events were included. Vitamin D supplementation reduced mortality among patients with COVID-19 patients, odd ratio, 2.31, 95% CI, 1.49–3.58; in addition, supplementation was effective in COVID-19 prevention, odd ratio, 1.92, 95% CI, 1.01–3.64.
Conclusion: Vitamin D supplementation prevented COVID-19 and increased survival among patients admitted with moderate/severe COVID-19.