Vitamin D Deficiency is Associated with Increased Severity of Dengue Fever
Emerging evidence suggests that vitamin D deficiency is associated with more severe dengue fever, particularly in children, though current guidelines do not recommend routine vitamin D screening or supplementation specifically for dengue prevention.
Key Evidence on the Association
The most recent and comprehensive evidence demonstrates a clear relationship between low vitamin D status and dengue severity:
A 2026 meta-analysis found vitamin D deficiency was associated with severe dengue, with a particularly striking effect in children (OR: 51.20,95% CI: 3.12-842.95) 1. When an outlier was excluded, the overall association remained significant (OR: 1.67,95% CI: 1.04-2.67).
A 2026 Vietnamese pediatric study showed serum 25(OH)D levels were independently and inversely associated with dengue severity, with each unit increase in vitamin D reducing severe dengue odds by 11% (adjusted OR: 0.89,95% CI: 0.85-0.93) 2. Importantly, this study found that vitamin D status mattered more than genetic VDR polymorphisms.
A 2025 Indian study demonstrated that lower 25(OH)D levels correlated with higher miRNA-155 expression and elevated inflammatory cytokines (TNF-α, IL-6, IFN-γ), suggesting a mechanistic link between vitamin D deficiency and excessive inflammation in severe dengue 3.
Clinical Implications
Who is at Risk?
Patients with vitamin D deficiency appear more susceptible to:
- Severe dengue manifestations (dengue hemorrhagic fever, dengue shock syndrome)
- Greater plasma leakage
- More severe thrombocytopenia
- Increased bleeding complications not fully explained by platelet counts 4
The Pediatric Population Deserves Special Attention
The association is particularly pronounced in children, where vitamin D deficiency may increase severe dengue odds by over 50-fold 1. This suggests pediatric dengue patients warrant closer monitoring of vitamin D status.
Guideline Context and Limitations
Current endocrine society guidelines (2024) do not support routine vitamin D screening in the general population without established indications 5. The U.S. Preventive Services Task Force similarly found insufficient evidence for routine vitamin D screening in asymptomatic adults 6.
However, these guidelines were not developed with dengue-endemic populations in mind and predate the most recent dengue-specific evidence.
Practical Approach
For Dengue-Endemic Regions:
- Consider vitamin D assessment in hospitalized dengue patients, especially children and those with warning signs
- Patients with 25(OH)D levels <20 ng/mL (deficient range) may warrant closer monitoring for progression to severe disease
- The median vitamin D level in dengue patients across studies was consistently in the deficient range (around 12 ng/mL) 7
Common Pitfalls to Avoid:
- Do not assume vitamin D supplementation will prevent or treat dengue - the current evidence is observational only, showing association not causation
- Do not delay standard dengue management while addressing vitamin D status
- Recognize that acute inflammation from dengue itself may affect vitamin D levels, making it unclear whether low levels are cause or consequence 6
Mechanistic Rationale
Vitamin D's immunomodulatory effects provide biological plausibility:
- Reduces pro-inflammatory cytokine production
- Modulates both innate and adaptive immune responses
- May limit viral replication in infected cells 3, 8
- Downregulates inflammatory miRNAs including miRNA-155 3
Evidence Gaps Requiring Caution
Prospective interventional trials are needed to establish whether vitamin D supplementation in deficient individuals can reduce dengue severity 1. All current evidence is observational and cross-sectional, limiting causal inference. The substantial heterogeneity between studies (I² = 61.6%) suggests population-specific factors may modify this relationship 1.
Until such trials are completed, vitamin D assessment and repletion in dengue patients should be considered supportive care rather than disease-modifying therapy, with primary focus remaining on standard fluid management, monitoring for warning signs, and appropriate escalation of care.