I do not understand what you mean with 'in reverse'. I am aware that there is no solid scientific evidence for a positive effect of vitamin D supplementation with respect to COVID-19, but I understand that the article does not exclude it. Yes, it does mention that treating people with high doses of vitamin D who are already seriously ill, has no significant effect. but that does not exclude the possibility that not having a vitamin D deficiency could prevent you from becoming seriously ill with certain types of infections.
I understand that there are some mechanism where vitamin D is linked to the immune system, as described in, for example: https://eje.bioscientifica.com/view/journals/eje/183/5/EJE-2...
