The vitamin D for COVID-19 (VIVID) trial: A pragmatic cluster-randomized design

Contemp Clin Trials. 2021 Jan;100:106176. doi: 10.1016/j.cct.2020.106176. Epub 2020 Oct 10.


Objectives: To determine the effect of vitamin D supplementation on disease progression and post-exposure prophylaxis for COVID-19 infection. We hypothesize that high-dose vitamin D3 supplementation will reduce risk of hospitalization/death among those with recently diagnosed COVID-19 infection and will reduce risk of COVID-19 infection among their close household contacts.

Methods: We report the rationale and design of a planned pragmatic, cluster randomized, double-blinded trial (N = 2700 in total nationwide), with 1500 newly diagnosed individuals with COVID-19 infection, together with up to one close household contact each (~1200 contacts), randomized to either vitamin D3 (loading dose, then 3200 IU/day) or placebo in a 1:1 ratio and a household cluster design. The study duration is 4 weeks. The primary outcome for newly diagnosed individuals is the occurrence of hospitalization and/or mortality. Key secondary outcomes include symptom severity scores among cases and changes in the infection (seroconversion) status for their close household contacts. Changes in vitamin D 25(OH)D levels will be assessed and their relation to study outcomes will be explored.

Conclusions: The proposed pragmatic trial will allow parallel testing of vitamin D3 supplementation for early treatment and post-exposure prophylaxis of COVID-19. The household cluster design provides a cost-efficient approach to testing an intervention for reducing rates of hospitalization and/or mortality in newly diagnosed cases and preventing infection among their close household contacts.

Keywords: COVID-19; Cluster randomization; Early treatment; Prophylaxis; SARS-CoV-2; Vitamin D.

Publication types

  • Clinical Trial Protocol
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • COVID-19 / mortality
  • COVID-19 Drug Treatment*
  • Comorbidity
  • Dietary Supplements*
  • Double-Blind Method
  • Hospitalization / statistics & numerical data
  • Humans
  • Middle Aged
  • Minority Groups / statistics & numerical data
  • Risk Factors
  • SARS-CoV-2
  • Seroconversion
  • Severity of Illness Index
  • Socioeconomic Factors
  • Vitamin D / therapeutic use*


  • Vitamin D