Abstract: Original Investigation | Infectious Diseases Assessment of the Association of Vitamin D Level With SARS-CoV-2 Seropositivity Among Working-Age Adults Yonghong Li, PhD; Carmen H. Tong, MS; Lance A. Bare, PhD; James J. Devlin, PhD Abstract Key Points IMPORTANCE Low vitamin D levels have been reported to be associated with increased risk of SARS-CoV-2 infection. Independent, well-powered studies could further our understanding of this association. Question Are low levels of vitamin D independently associated with the risk of SARS-CoV-2 seropositivity? Findings In this cohort study of 18 148 OBJECTIVE To examine whether low levels of vitamin D are associated with SARS-CoV-2 individuals whose vitamin D levels were seropositivity, an indicator of previous infection. measured before the COVID-19 pandemic, low levels of vitamin D were DESIGN, SETTING, AND PARTICIPANTS This is a cohort study of employees and spouses who associated with SARS-CoV-2 elected to be tested for SARS-CoV-2 IgG as part of an annual employer-sponsored health screening seropositivity in unadjusted univariable program conducted in August to November 2020. This program includes commonly assessed analysis. However, after adjusting for demographic, biometric, and laboratory variables, including total vitamin D measurement. Baseline potentially confounding factors, (prepandemic) levels of vitamin D and potential confounders were obtained from screening results including age, sex, race/ethnicity, from the previous year (September 2019 to January 2020). Data analysis was performed from education, body mass index, blood December 2020 to March 2021. pressure, smoking status, and geographical location, vitamin D level EXPOSURES Low total serum 25-hydroxyvitamin D, defined as either less than 20 ng/mL or less was not associated with SARS-CoV-2 than 30 ng/mL. seropositivity. Meaning Although SARS-CoV-2– MAIN OUTCOMES AND MEASURES The main outcome was SARS-CoV-2 seropositivity, as determined with US Food and Drug Administration emergency use–authorized assays. The seropositive individuals did have lower vitamin D levels than seronegative association of SARS-CoV-2 seropositivity with vitamin D levels was assessed by multivariable logistic regression analyses and propensity score analyses. individuals, low vitamin D levels were not independently associated with the risk of seropositivity. RESULTS The 18 148 individuals included in this study had test results for SARS-CoV-2 IgG in 2020 and vitamin D levels from the prepandemic and pandemic periods. Their median (interquartile range) age was 47 (37-56) years, 12 170 (67.1%) were women, 900 (5.0%) were seropositive, 4498 (24.8%) had a vitamin D level less than 20 ng/mL, and 10 876 (59.9%) had a vitamin D level less than 30 ng/mL before the pandemic. In multivariable models adjusting for age, sex, race/ethnicity, education, + Invited Commentary + Supplemental content Author affiliations and article information are listed at the end of this article. body mass index, blood pressure, smoking status, and geographical location, SARS-CoV-2 seropositivity was not associated with having a vitamin D level less than 20 ng/mL before (odds ratio [OR], 1.04; 95% CI, 0.88-1.22) or during (OR, 0.93; 95% CI, 0.79-1.09) the pandemic; it was also not associated with having a vitamin D level less than 30 ng/mL before (OR, 1.09; 95% CI, 0.93-1.27) or during (OR, 1.05; 95% CI, 0.91-1.23) the pandemic. Similar results were..