About this Research Topic
A year has now passed since the new disease Covid-19 started to spread throughout all parts of the world. The new species of Coronaviridae, named SARS-CoV-2, and particularly new variants, are highly contagious, thus causing a rapidly evolving pandemic. Around 80% of people who are infected by SARS-CoV-2 are either asymptomatic or just experience mild symptoms; the remaining 20% have severe symptoms. For 1% of infected people the outcome is fatal. So far, the most important factor that correlates with the severity of disease symptoms is old age. Elderly individuals, particularly those with underlying morbidities, are the most likely to develop life-threatening complications, and to die from Covid-19 disease. Schoolchildren are mostly asymptomatic, and highly unlikely to die.
Recent studies have shown that the low level of vitamin D in the blood serum of infected persons correlates with the severity of Covid-19 disease. The major and the best-known role of the vitamin’s D most active metabolite 1,25-dihydroxyvitamin D (1,25D) is that it maintains the calcium-phosphate homeostasis of the organism. However, 1,25D also regulates other vital processes. These include detoxification of the organism, the differentiation of keratinocytes, and functioning of immune cells. 1,25D affects the development and/or function of cells of both the innate and adaptive immune systems, such as macrophages, dendritic cells, neutrophils, T and B lymphocytes. This therefore highlights the need to verify whether 1,25D is indeed a causal factor that influences infection by SARS-CoV-2 and/or the course of disease, or just one of many factors that has been correlated by chance.
Within this Research Topic, we aim to discuss whether 1,25D helps the human immune system to protect against and/or fight off infections caused by SARS-CoV-2, and by other respiratory viruses. Studies of the mechanisms that might explain the potential role of 1,25D in preventing infection by the virus and/or eliminating the virus, without producing harm to the human body such as a cytokine storm are needed. We welcome reports of studies that have carefully dissected the importance to Covid-19 infection and disease of 1) the levels of vitamin D in the serum, 2) the levels of its active metabolite 1,25D inside the cells, and 3) the actions of the vitamin D receptor (VDR) that is activated by 1,25D. We thus welcome reports of cases of Covid-19 infections in patients who carry mutations in either the VDR gene or the gene which encodes the enzyme that activates vitamin D to 1,25D. In addition, reports of recent epidemiological studies and proposals of the future prospective studies are needed to distinguishing real causation from correlations that have no causative link.
We would like to encourage a broad spectrum of researchers to contribute to this Research Topic to open the discussion about the possible relevance of vitamin D supplementation for respiratory tract infections. Our Research Topic welcomes submissions of Original Research, Hypotheses, Perspectives, Reviews, and Commentaries articles focused on the following topics, but not limited to:
• Analysis of clinical studies in patients with Covid-19, or other viral infections, in relation to patients’ vitamin D status.
• Results from research that could explain the beneficial effects of 1,25D in patients with viral infections.
• Critical analyses of previously published research.
• Case reports on patients with Covid-19, and who carry mutations in vitamin D system genes.
• Proposals for future clinical studies.
• New methodologies that could be used in the statistical analysis of the available data.
Keywords: SARS-CoV-2, vitamin D, deficiency, symptoms, outcome
Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.