Efficacy of vitamin D replacement therapy on 28 cases of myalgic encephalomyelitis/chronic fatigue syndrome after COVID-19 vaccination.
Kodama, Shinichiro, Konishi, Nafuko, Hirai, Yuriko et al. · Nutrition (Burbank, Los Angeles County, Calif.) · 2025 · DOI
Quick Summary
This study looked at 28 patients who developed ME/CFS after COVID-19 vaccination and found that most had very low vitamin D levels. When these patients received vitamin D treatment through diet, sun exposure, and supplements, their vitamin D levels improved and their ME/CFS symptoms significantly decreased—with 82% of patients no longer meeting ME/CFS criteria after treatment. Sleep problems and autonomic symptoms (like heart rate and blood pressure changes) showed the most improvement.
Why It Matters
This is one of the first studies systematically examining vitamin D status in post-vaccination ME/CFS and showing potential symptomatic benefit from replacement therapy. The finding that 82% of patients experienced remission from ME/CFS criteria following vitamin D treatment offers hope for a potentially modifiable factor in a subset of post-vaccination ME/CFS cases and may inform future mechanistic investigations and clinical trials.
Observed Findings
27 of 28 patients (96%) had insufficient or deficient vitamin D levels at baseline (mean 16 ± 4 ng/mL).
Following vitamin D replacement therapy, mean serum vitamin D increased to 28 ± 5 ng/mL.
23 of 28 patients (82%) no longer met ME/CFS diagnostic criteria after treatment.
ME/CFS diagnostic symptom scores decreased from 10.3 ± 2.1 to 3.3 ± 2.0.
Sleep problems showed the greatest symptomatic improvement (71%), followed by autonomic symptoms (68%).
Inferred Conclusions
Vitamin D deficiency is highly prevalent in patients who develop ME/CFS following COVID-19 vaccination.
Appropriate vitamin D replacement therapy may lead to significant symptomatic relief and potential remission from ME/CFS criteria in deficient patients.
Vitamin D repletion may be particularly effective for autonomic and sleep dysfunction in post-vaccination ME/CFS.
Remaining Questions
Does vitamin D deficiency play a causal role in post-vaccination ME/CFS, or is it an associated finding? What is the prevalence of vitamin D deficiency in ME/CFS populations without post-vaccination onset, and does treatment similarly improve outcomes?
How durable are the improvements observed, and what percentage of patients maintain remission at long-term follow-up?
What This Study Does Not Prove
This study does not prove that vitamin D deficiency causes ME/CFS, only that correction of deficiency was associated with symptom improvement in this specific group. The lack of a control group, randomization, or blinding means we cannot exclude placebo effects, natural recovery, or confounding factors. Results apply only to ME/CFS patients with documented vitamin D deficiency; generalizability to all ME/CFS populations is unknown.