For immunity, you can’t go past garlic (raw or ‘aged’ encapsulated). Add crushed garlic to salad dressings or make a garlic aoli with organic egg and cold pressed olive oil. I even throw whole cloves through my juicer to my green juice. Also, coconut oil is strongly anti-microbial. Also great are onions, Ginger and ‘probiotic foods’ like raw sauerkraut and kefir. And avoidance of all sugars is really important.