Background: Several studies have examined Vitamin D deficiency (VDD) and the effects of vitamin D therapy in patients with coronavirus disease 2019 (COVID-19). However, a bibliometric assessment of research output on VDD in relation to COVID-19 is unavailable. Materials and Methods: We searched Elsevier’s Scopus database for publications on VDD in COVID-19 using a defined search strategy. Data pertaining to the growth of publications, citation metrics, the most active countries, institutions, authors, journals, and the most cited articles, were analyzed using appro-priate bibliometric tools. Mapping of keywords was done to identify the research trends. Results: Of 435 global publications on VDD in COVID-19, 187 (42.9%) were original articles. The total and average citations per paper (CPP) were 5664 and 13.0, respectively. Eighty-eight (20.2%) publications were funded; the National Institute of Health, USA, was the leading funding agency (n=18). Seventy-four countries participated in research on this theme; the USA and Italy with 18.3% and 16.5% led in productivity, whereas Ireland and the USA were the most impactful. The most dominant research topic was “Risk Factors” with 29.6% share, fol-lowed by “Epidemiology” (27.3%), “Complications” (26.4%), “Clinical studies” (24.8%), and “Pathophysiology” (17.2%), only 14.0% studies were on “Treatment”. The research patient populations were “Adults”, “Aged,” and “Middle-Aged,” with 24.1%, 21.6%, and 17.7% share, respectively; only 6.4% studies involved children. The organizations and authors numbered 254 and 383, respectively; Trinity College, Dublin, Ireland, and Harvard Medical School, USA, were the most productive, whereas St. James’s Hospital, Ireland, and University Hospital Brigham, UK were the most impactful. Belgium’s Delanghe and Ireland’s Kenny were the top productive authors, and Grant (USA) and Laird (Ireland) were the most influential. Journal of Medical Virology and Endocrine lead productivity while Aging Clinical and Experimental Research and Diabetes and Metabolic Syndrome: Clinical Research and Review lead in impact. Conclusion: The research on VDD in relation to COVID-19 has primarily been conducted in high-income countries, with the USA, Italy, and UK accounting for almost 50% of total publication output. The research gaps appear to be treatment-related aspects and VDD in children with COVID-19. Our assessment of the current status of research on VDD in COVID-19 may help the research community and policy-makers to prioritize research needs in this field.
Key words: Coronavirus disease 2019, Vitamin D Deficiency, Bibliometrics, Research impact, Scientometrics, Children.