Micro-nutrients, which include many vitamins, and minerals are imperative to maintain good health. I am of the opinion that micro-nutrients that boost the immunity should be included in our diet. The person with strong immune system can hardly get infection.

See a paper by Harthill (2011), who found that when micronutrient such as selenium (Se) deficient virus-infected hosts (including Ebola hemorrhagic fevers) were supplemented with dietary Se, viral mutation rates diminished and immunocompetence improved.

Reference

Harthill M.2011.Review: micronutrient selenium deficiency influences evolution of some viral infectious diseases.Biol Trace Elem Res. 143(3):1325-36. doi: 10.1007/s12011-011-8977-1. Epub 2011 Feb 12.

This selenium reference is very, very interesting. In addition however, I would like to just urge that an evolutionary, broader health perspective be considered: we have evolved to need at least 50 known micronutrients (vitamins, minerals amino acids, and essential fatty acids) --- so broad spectrum for general health and immunity makes sense.

Vitamin D is able to built up immune systems in one week so as to fight .enveloped viruses similar to Ebola. I am actively trying to get a lot of vitamin D to Liberia to confirm that it prevents Ebola as well.  I run the world's largest Vitamin D website. vitamindwiki.com

http://vitamindwiki.com/tiki-index.php?page_id=5833

People who focus on a single nutrient just do not understand metabolism, or indeed evolution. There is no single nutrient that is a solution to complex health problems. Any given metabolic pathway is dependent on enzymes whose efficiency is a function of cofactor micronutrients --- MANY of them. So of course provide vitamin D. But what about all the other vitamins and minerals and amino acids and phytonutrients? The most efficient approach to a complex health problem is broad spectrum. Anything else is simply a reflection of the western attitude of looking for magic bullets.