SynthesisEpidemiology and health2021
The role of vitamin D deficiency on COVID-19: a systematic review and meta-analysis of observational studies.
Synthesis in Epidemiology and health, 2021. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 44 papers, 5 of them syntheses that pooled it.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
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Who cites it
44 citing papers in PubMed, 5 syntheses or guidelines pooled it, 104 citations in OpenAlex.
- A Systematic Review of Vitamin D Supplementation in Oncology: Chance of Science or Effectiveness?Nutrients · 2025Pooled it
- Vitamin D Deficiency Meets Hill's Criteria for Causation in SARS-CoV-2 Susceptibility, Complications, and Mortality: A Systematic Review.Nutrients · 2025Pooled it
- The role of vitamin D in outcomes of critical care in COVID-19 patients: evidence from an umbrella meta-analysis of interventional and observational studies.Public health nutrition · 2024Pooled it
- Serum vitamin D levels and COVID-19 during pregnancy: A systematic review and meta-analysis.Clinical nutrition ESPEN · 2022Pooled it
- Administration of vitamin D and its metabolites in critically ill adult patients: an updated systematic review with meta-analysis of randomized controlled trials.Critical care (London, England) · 2022Pooled it
- Prevention of covid-19 and other acute respiratory infections with cod liver oil supplementation, a low dose vitamin D supplement: quadruple blinded, randomised placebo controlled trial.BMJ (Clinical research ed.) · 2022Trial
- Trial
- Vitamin D and COVID-19: Inmunomodulatory Effects and the Mexican Public Health Perspectives.International journal of molecular sciences · 2026Review
- Vitamin D in Infectious Diseases: A Narrative Review Focusing on COVID-19, Long COVID, and Influenza.Nutrients · 2026Review
- Association between vitamin D and COVID-19 infection and mortality in Taiwanese patients.Journal of the Chinese Medical Association : JCMA · 2025Article
- Voluntary vitamin D testing: a decade-long study of utilisation patterns and impact on deficiency outcomes in Taiwan.Public health nutrition · 2025Article
- A scoping review: the impact of nutritional status on the efficacy, effectiveness, and immunogenicity of COVID-19 vaccines.Tropical diseases, travel medicine and vaccines · 2025Review
- Vitamin D Status and Incidence of SARS-CoV-2 Reinfections in the Borriana COVID-19 Cohort: A Population-Based Prospective Cohort Study.Tropical medicine and infectious disease · 2025Article
- Evaluation of vitamin D status, vitamin D receptor expression, and innate immune mediators in COVID-19.Frontiers in endocrinology · 2025Observational
- Comparison of the role of vitamin D in normal organs and those affected by COVID-19.International journal of medical sciences · 2025Review
- Association between vitamin D deficiency and clinical outcome in patients with COVID-19 in the post-Omicron phase.Frontiers in nutrition · 2025Article
- Vitamin D deficiency may increase the risk of acute kidney injury in patients with diabetes and predict a poorer outcome in patients with acute kidney injury.BMC nephrology · 2024Article
- Investigation of the Relationship between Vitamin D Deficiency and Vitamin D-Binding Protein Polymorphisms in Severe COVID-19 Patients.Diagnostics (Basel, Switzerland) · 2024Article
- Early Metabolomic and Immunologic Biomarkers as Prognostic Indicators for COVID-19.Metabolites · 2024Article
- Vitamin D Metabolism Parameters and Cytokine Profile in COVID-19 Patients with Bolus Cholecalciferol Supplementation.Diagnostics (Basel, Switzerland) · 2024Article
Corrections and comments
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Authors and funding
3 authors at 1 institution in 1 country.
Funding
No grant is acknowledged in the PubMed record.
Abstract
objectivesAlthough vaccination has started, coronavirus disease 2019 (COVID-19) poses a continuing threat to public health. Therefore, in addition to vaccination, the use of supplements to support the immune system may be important. The purpose of this study was to synthesize evidence on the possible effect of low serum vitamin D levels (25[OH]D<20 ng/mL or 50 nmol/L) on COVID-19 infection and outcomes.
methodsWe searched Google Scholar, PubMed, Scopus, Web of Science, and ScienceDirect without any language restrictions for articles published between January 1 and December 15, 2020. We performed 3 meta-analyses (called vitamin D and COVID-19 infection meta-analysis [D-CIMA], vitamin D and COVID-19 severity meta-analysis [D-CSMA], and vitamin D and COV ID-19 mortality meta-analysis [D-CMMA] for COVID-19 infection, severity, and mortality, respectively) to combine odds ratio values according to laboratory measurement units for vitamin D and the measured serum 25(OH)D level.
resultsTwenty-one eligible studies were found to be relevant to the relationship between vitamin D and COVID-19 infection/outcomes (n=205,869). The D-CIMA meta-analysis showed that individuals with low serum vitamin D levels were 1.64 times (95% confidence interval [CI], 1.32 to 2.04; p<0.001) more likely to contract COVID-19. The D-CSMA meta-analysis showed that people with serum 25(OH)D levels below 20 ng/mL or 50 nmol/L were 2.42 times (95% CI, 1.13 to 5.18; p=0.022) more likely to have severe COVID-19. The D-CMMA meta-analysis showed that low vitamin D levels had no effect on COVID-19 mortality (OR, 1.64; 95% CI, 0.53 to 5.06, p=0.390).
conclusionsAccording to our results, vitamin D deficiency may increase the risk of COVID-19 infection and the likelihood of severe disease. Therefore, we recommend vitamin D supplementation to prevent COVID-19 and its negative outcomes.
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Registered trials
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