The NIH and Martineau articles assume that 10ng/ml is an adequate level of 25OHD, the form of vitamin D stored in the blood and which controls the concentration of 25OHD required for autocrine signalling in many types of cells - especially those of the immune system.  Much better guidance for the desired level of 40 to 60ng/ml (100 to 150nmol/L) comes from articles such as https://doi.org/10.3390/nu12072097 .

One of the most pertinent items of research describes Th1 lymphocytes isolated from the lungs of patients with severe COVID-19 symptoms having an autocrine signaling pathway which should be activated, to turn the cells off their hyper-inflammatory program which produces pro-inflammatory IL-17 and instead make them produce the anti-inflammatory cytokine IL-10.  However, this anti-inflammatory pathway is not working, due to lack of 25OHD.  It works fine in the same lymphocytes from healthy controls.  The researchers do not report the 25OHD levels of the patients or controls so I wrote a question about this at the preprint page: www.biorxiv.org/.../2020.07.18.210161v1