A systematic review and meta-analysis of effect of vitamin D levels on the incidence of COVID-19

This meta-analysis reported that there is a connection between vitamin D status and COVID-19. Clinical trials are needed to establish if supplementation is warranted.

To determine any connection between vitamin D status and COVID-19 infection

Mean vitamin D levels in SARS-CoV-2 negative patients was 17.7 ± 6.9 ng/mL compared to SARS-CoV-2 positive patients 14.1 ± 8.2 ng/mL (MD = 3.93; 95% CI 2.84–5.02; I² = 99%; p < 0.001).

Thirteen studies with data for 14,485 participants. 3 studies were performed in United Kingdom, 2 studies in Iran, 2 in Saudi Arabia, 2 in Italy, and 1 in each of the following countries: Spain, Republic of Korea, Israel and China.

• It is important to consider that the studies included are limited to the inclusion/exclusion criteria of the study design and, therefore, may miss important studies with slightly different design, but meaningful data.
• In addition, in order to conduct a meta-analysis the studies included must have similar endpoints to extract and, in doing so, researchers may group together studies that are not the same, but will be analyzed as the same which can lead to skewed conclusions.
• A meta-analysis only includes studies that have been published and, therefore, information gathered may be subject to publication bias. This means that studies that show no effect or the opposite of the expected effect may not be published and, therefore, not included.

Low serum vitamin D level is statistically and significantly associated with the risk of COVID-19 infection. Supplementation of vitamin D especially in deficiency risk groups is indicated.

• This was a systematic review and meta-analysis which followed the established Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) Guidelines.
• Before starting the literature review, search methods as well as criteria for which studies to include and exclude were established.
• On May 10, 2021, a systematic review was carried out by 2 authors using PubMed, EMBASE, Web of Science, Cochrane Collaboration Databases and Scopus electronic databases. The search was performed using the following terms: “25-hydroxyvitamin D” OR “25(OH)D” OR “vitamin D” AND “coronavirus” OR “SARS- -CoV-2” OR “COVID-19”. A manual search of references listed in reviews and reports was also performed. Only full articles in the English language were included.
• For the meta-analysis, the following information was extracted from each included study: the first author’s name, year of publication, study design, country, sample size, age, gender, vitamin D level in SARS-CoV-2 positive and negative patients. Mean differences (MDs) with their 95% confidence intervals (CI) were calculated.
• Bias of the included studies used the revised tool for risk of bias in randomized trials — RoB 2 tool was used to assess the quality of randomized studies.

Szarpak L, Rafique Z, Gasecka A, Chirico F, Gawel W, Hernik J, Kaminska H, Filipiak KJ, Jaguszewski MJ, Szarpak L. A systematic review and meta-analysis of effect of vitamin D levels on the incidence of COVID-19. Cardiol J. 2021 Jul 26. doi: 10.5603/CJ.a2021.0072. Epub ahead of print. PMID: 34308537.