Prospective study of vitamin D levels and COVID-19 infection in the Black Women's Health Study, showing higher risk of infection for lower vitamin D levels. Vitamin D levels were from 3-7 years before infection. Levels at the time of infection may differ, which may reduce the size of the effect observed.
Cozier et al., 7/27/2021, prospective, USA, North America, peer-reviewed, 6 authors.
risk of COVID-19 case, 38.6% lower, RR 0.61, p = 0.02, high D levels 94 of 1601 (5.9%), low D levels 33 of 373 (8.8%), adjusted per study, odds ratio converted to relative risk, >20ng/mL, multivariable.
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.