Vitamins alleviate COVID-19?

A Swedish chief physician, Professor Urban Alhagen, has together with an international research team written a review article: Nutritional Interventions with Zinc, Selenium and Vitamin D for Raising Anti-Viral Resistance Against Progressive COVID-19 

The article concludes that treatment with zinc, selenium and vitamin D has an immune-boosting and anti-inflammatory effect and therefore can protect against SARS-CoV2 and alleviate covid-19. 

There are numerous scientific studies on the beneficial effects of nutrients for COVID patients. Conversely, for example, a Spanish study found vitamin D deficiency in 80 percent of covid-19 patients in hospitals. 
https://academic.oup.com/jcem/advance-article/doi/10.1210/clinem/dgaa733/5934827