Among patients admitted with laboratory-confirmed  COVID-19, low serum vitamin D [25(OH)D] levels were associated with greater in-hospital mortality and need for invasive mechanical ventilation...

This study of 204 patients, suggests that adequate (25(OH)D of >50 nmol/L) levels of vitamin D may play a role in inflammation and reduce the severity of COVID-19.

After adjusting for demographic variables and comorbidities, this retrospective analysis of COVID-positive patients in New York City, shows a significant association between low 25(OH)D levels and an increased likelihood of need for oxygen support.

In this 154 patient prospective cohort study in India, individuals with severe COVID-19 had lower vitamin D levels and were more likely to be vitamin D deficient.  Deficient patients were more likely to pass...

This 129 person cohort study conducted in Italy did not report a relationship between vitamin D levels and health outcomes in the enrolled COVID-19 population.

In this small, case control study conducted in China there was an association between vitamin D deficiency and COVID-19, especially in severe cases.

In this cohort study of 489 patients who had a vitamin D level measured in the year before COVID-19 testing, the relative risk of testing positive for COVID-19 was 1.77 times greater for patients with likely deficient vitamin D status compared...

Plasma 25(OH)D levels less than 75 nmol/L appear to be an independent risk factor for COVID-19 infection and hospitalization in the Israeli population.

In this small, quasi experimental study, elderly, frail nursing home residents in France diagnosed with COVID-19 who were given a high, single dose of vitamin D during or just before COVID-19 infection experienced an improved survival rate...