Health Business News - Vitamin D could help play a key role in the prevention and treatment of COVID-19, say health experts. The prohormone has been studied in the treatment of other respiratory diseases, offering the potential to boost antiviral immune responses and dampen harmful inflammation. Links have been established between a deficiency of vitamin D and critically ill COVID-19 patients and a deficiency noted in many populations most at risk from the virus, such as the BAME community.