RT Journal Article SR Electronic T1 Serious vitamin D deficiency in healthcare workers during the COVID-19 pandemic JF BMJ Nutrition, Prevention & Health JO BMJ Nutrition FD BMJ Publishing Group Ltd SP e000364 DO 10.1136/bmjnph-2021-000364 A1 Funaki, Takanori A1 Sanpei, Makiko A1 Morisaki, Naho A1 Mizoue, Tetsuya A1 Yamaguchi, Koushi YR 2022 UL http://nutrition.bmj.com/content/early/2022/01/03/bmjnph-2021-000364.abstract AB