NorthWest Biotherapeutics Inc (NWBO)

[longfellow95]

Studies have shown that selenium is important in the stimulation of antibodies, which are elements of the immune system that seek out and destroy viral, bacterial, fungal, and protozoan foreign bodies that result in diseases and infections. It is said to help stimulate these antibodies, particularly after you receive a vaccination for one of these diseases, making your body resilient and experienced in fighting them off so you remain healthy and protected throughout your life.

https://www.organicfacts.net/selenium.html

(Although most of these 'benefits of selenium' web sites are basically advertising, there is a body of solid evidence behind selenium benefits. As there is for Vit D, and Zinc.)

But if you eat a lot of oysters and brazil nuts, you won't need to supplement your Selenium intake.