Reducing Risks from COVID-19: Cost-Effective Ways of Strengthening Individual's and the Population Immunity with Vitamin D

In addition to being involved in the regulation of calcium and phosphate metabolism and the musculoskeletal functions, vitamin D has immune modulatory effects through several independent pathways. Its active hormone, calcitriol [1,25(OH)2D] effect both innate and adaptive immune systems essential for optimal immune functions. Vitamin D deficiency exacerbates immune-related disorders, including type 1 diabetes, multiple sclerosis, rheumatoid arthritis, psoriasis, respiratory infections, including COVID-19. In those with COVID-19, complications and the number of deaths is higher in those who are older than 70 years, persons with a darker skin colour and/or ethnic minorities living in colder climatic regions, institutionalized persons, and with pre-existing chronic diseases. These groups of people have exceedingly high prevalence of severe vitamin D deficiency and thereof weaker immune systems. Collectively, these increases the vulnerability to microbial infections, particularly respiratory viruses, and for developing severe complications and deaths. Vitamin D related immune protective effects includes, the generation of anti-microbial peptides cathelicidin and defensins and antibodies against invading pathogens; the initiation of immune defences via natural killer cells, macrophages, and epithelial cells; the enhanced expression of angiotensin-converting enzyme 2 (ACE-2) and diminish expression of inflammatory cytokines; and reduce replication and enhance elimination of viruses from the body. The severity of complications and deaths associated with COVID-19 markedly increases in the presence of severe hypovitaminosis D: serum 25(OH)D concentration of less than 10 ng/mL. Excess complications and deaths from COVID-19 can be cost-effectively prevented with rapidly boosting the immunity using upfront loading, high doses of vitamin D; this will create an equivalent of internal “body armour”-defence system, that protects against COVID-19.