Survey analysis of dietary supplements showing vitamin D usage associated with lower incidence of COVID-19. These results are for PCR+ cases only, they do not reflect potential benefits for reducing the severity of cases. A number of biases could affect the results, for example users of the app may not be representative of the general population, and people experiencing symptoms may be more likely to install and use the app.
Louca et al., 11/30/2020, retrospective, population-based cohort, United Kingdom, Europe, peer-reviewed, 26 authors, dosage not specified.
risk of COVID-19 case, 7.5% lower, RR 0.92, p < 0.001, odds ratio converted to relative risk, United Kingdom, all adjustment model.
Effect extraction follows pre-specified rules
prioritizing more serious outcomes. For an individual study the most serious
outcome may have a smaller number of events and lower statistical signficance,
however this provides the strongest evidence for the most serious outcomes
when combining the results of many trials.