Association Between Vitamin D Deficiency and COVID-19 Incidence, Complications, and Mortality in 46 Countries: An Ecological Study

Health Secur. May-Jun 2021;19(3):302-308. doi: 10.1089/hs.2020.0137. Epub 2020 Dec 14.


Each patient's immune defenses play a major role in mitigating the impact (ie, morbidity and mortality) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for coronavirus disease 2019 (COVID-19). Vitamin D is an important modulator of the immune system. Although serum 25-hydroxyvitamin D levels can be raised through diet or supplements, most vitamin D in the body is the result of dermal synthesis from ultraviolet radiation. The production of vitamin D in the skin, however, can be limited by latitude, skin-covering clothes, the use of sunblock, and skin pigmentation. Vitamin D deficiency affects a high percentage of the world population. Serum 25-hydroxyvitamin D levels are suboptimal, not only in specific risk groups but also in adults from many countries. Low vitamin D levels, therefore, represent a risk factor for several different pathologies, including SAR-CoV-2. This study used an ecological design to assess the association between vitamin D deficiency and COVID-19 incidence, complications, and mortality across 46 countries. All data were obtained from published sources. The results of the study suggest an association at the population level between the prevalence of vitamin D deficiency and the risk of being infected with COVID-19, severity of the disease, and risk of dying from it.

Keywords: COVID-19; Infectious disease; Public health preparedness/response; SARS; Vitamin D.

MeSH terms

  • COVID-19 / blood
  • COVID-19 / mortality*
  • COVID-19 / prevention & control
  • Dietary Supplements / statistics & numerical data
  • Humans
  • Incidence
  • Vitamin D / analogs & derivatives
  • Vitamin D / blood
  • Vitamin D / therapeutic use*
  • Vitamin D Deficiency / blood
  • Vitamin D Deficiency / mortality*
  • Vitamin D Deficiency / prevention & control
  • Vitamins / therapeutic use*


  • Vitamins
  • Vitamin D
  • 25-hydroxyvitamin D