N/A
Completed N=923
Low vs. Moderate to High Dose Vitamin D for Prevention of COVID-19
Source: ClinicalTrials.gov NCT04868903 ↗Enrolled (actual)
923
Serious AEs
0.0%
Results posted
Dec 2025
Primary outcomePrimary: SARS-CoV-2 Infection as Measured by Patient Report of Clinically Confirmed COVID-19 (or Viral PCR When Available) — 68; 50; 48; 30 Participants — p=0.10
Summary
The purpose of this study is to compare the risks of COVID-19 in individuals from Chicagoland communities randomized to low (400 IU/day) vs. moderate (4,000 IU/day) or high (10,000 IU/day) dose vitamin D.
Outcome Measures
| Outcome | Result | p-value |
|---|---|---|
| PRIMARY SARS-CoV-2 Infection as Measured by Patient Report of Clinically Confirmed COVID-19 (or Viral PCR When Available) |
68; 50; 48; 30; 20; 20 | 0.10 |
Eligibility Criteria
Subjects are able to participate if they:
- Are 18 years or older.
- Live or work in the Chicagloland area (Illinois counties: Cook, Lake, McHenry, DuPage, Kane, Kendall, Grundy, Will, and Kankakee; Indiana counties: Lake and Porter).
- Are interested in vitamin D as a potential preventive measure against COVID-19 in which they self-administer a daily dose of vitamin D during the 9-month study period.
- Are willing to attend the laboratory for drop-in appointments at UChicago Medicine or Rush University Medical Center every 3 months at 4 time points over a 9-month period for blood draws measuring COVID-19 antibodies, calcium, vitamin D and PTH levels.
- Are willing to complete self-report measures at 4 time points over the course of 9 months by completing a 15-minute survey at intake by telephone or via web and 10-minute web-based follow-up surveys.
Subjects are excluded from study participation if they:
- Report ever having a positive COVID-19 PCR test result
- Report being pregnant, planning to become pregnant, and/or report breastfeeding during the study period.
- Report a history of chronic kidney disease, including a history of abnormal GFR and/or creatinine.
- Report a history of hyperparathyroidism.
- Report a history of increased falls.
- Report a history of hypercalcemia.
- Report a history of gastrointestinal absorptive disorders, including having undergone bariatric surgery.
- Report a history of kidney stones (1 in past year or 2 in lifetime).
- Report already taking more than 400 IU of vitamin D daily as recommended by their health care provider, excluding multivitamins and excluding supplements that include vitamin D and calcium together.
- Report taking D2.
- Report a history of sarcoidosis.
- Screen positive for hypercalcemia during the initial blood test or follow-up blood tests.
- Screen positive for primary hyperparathyroidism during the initial blood test.
- Screen positive for COVID-19 antibodies during the initial blood test.
- Have vitamin D levels of >100ng/mL at study start, or >250ng/mL during follow-up labs.
- Are unwilling to provide blood samples during quarterly blood tests.
- Are unwilling to take daily vitamin D.
Data sourced from ClinicalTrials.gov (NCT04868903). Outcome figures and adverse-event rates are extracted automatically from the registry's posted results and are provided for clinician reference, not as a substitute for the primary publication. Informational only — not medical advice.