The purpose of this study is to compare the risks of COVID-19 in individuals from theChicagoland area and other communities in the United States randomized to low (400IU/day) versus moderate (4,000 IU/day) dose vitamin D.
This study will recruit 2,000 subjects from the Chicagoland area and across the United
States to participate in the study from home. Subjects will be invited to volunteer to
participate in the study through a variety of forms of outreach, mainly online (e.g.,
press releases, news interviews, social media, emails, etc.). The sample size was chosen
to have at least 80% power to detect a 20% or larger decrease in the hazard of developing
COVID-19 between study arms at p<0.05, based on an estimated monthly incidence of
COVID-19 (3%/month for Black/Latinx persons and 1%/month for White persons) and an
estimated fraction of persons already immune but unaware they have had COVID-19 (≤10%).
Subjects will take a daily dose of vitamin D and answer surveys about COVID-19 diagnosis
and symptoms over 12 months after enrollment.
Our overall aim is to compare the risks of COVID-19 in adults at increased risk of
COVID-19 randomized to low (400 IU/day) versus moderate (4,000 IU/day) dose vitamin D.
Our specific aims are:
Aim 1: To compare the risk of developing COVID-19 in adults at increased risk of COVID-19
randomized to low versus moderate dose vitamin D. We hypothesize that moderate dose
therapy will reduce rates of COVID-19 compared to low dose therapy because vitamin D will
reduce symptomatic infection that prompts testing for COVID-19.
Aim 2: To compare COVID-19 outcomes (symptoms, hospitalization, ICU stay, ventilator use,
death) in adults at increased risk of COVID-19 randomized to low vs. moderate dose
vitamin D. Consistent with several recent observational analyses, we expect higher doses
to improve COVID-19 outcomes.
Subjects will be asked to complete a web-based survey at intake and at 3, 6, 9, and 12
months after enrollment. The intake survey will collect baseline data on subjects'
current medications and supplements, sun exposure, exercise, diet and sleep habits,
possible COVID-19 symptoms, other influenza-like symptoms, previous exposures to
COVID-19, occupation, demographic information, and risks of exposure. The surveys at 3,
6, 9, and 12 months after enrollment will ask the participant or a proxy whether the
participant has had a clinically confirmed diagnosis of COVID-19 and the date if so, ask
about rates of study medication adherence, and assess for changes in the intake questions
about use of other supplements, sun exposure, diet, exercise, and COVID-19 exposures. If
the subject reports to have had COVID-19, we will ask about severity, including symptoms,
hospitalization and duration, ICU use and duration, need for mechanical ventilation and
duration, and death.
Dietary Supplement: Vitamin D 400IU
Low dose vitamin D (400 IU/day)
Other Name: Vitamin D3
Dietary Supplement: Vitamin D 4000IU
Moderate dose vitamin D (4000 IU/day)
Other Name: Vitamin D3
Inclusion Criteria:
Subjects are able to participate if they:
1. Are 18 years or older.
2. Live in the United States.
3. 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 12-month study
period.
4. Are willing to complete self-report measures at 5 time points over the course of 12
months by completing a 15-minute survey at intake via web and 10-minute web-based
follow-up surveys.
Exclusion Criteria:
Subjects are excluded from study participation if they:
1. Report being pregnant, planning to become pregnant, and/or report breastfeeding
during the study period.
2. Report a history of chronic kidney disease, including a history of abnormal GFR
and/or creatinine.
3. Report a history of hyperparathyroidism.
4. Report a history of increased falls.
5. Report a history of hypercalcemia.
6. Report a history of gastrointestinal absorptive disorders, including having
undergone bariatric surgery.
7. Report a history of kidney stones (1 in past year or 2 in lifetime).
8. 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.
9. Report taking D2.
10. Report a history of sarcoidosis.
University of Chicago
Chicago 4887398, Illinois 4896861, United States
David O Meltzer, MD, PhD, Study Director
University of Chicago