Vitamins C & D are important immuno-boosters. Vitamins A & B are also helpful, as is Zinc and selenium.
I take all of the above, along with garlic, turmeric and ginger.
Rda of course. The spices are great forms of antibiotic, antifungal, antioxident and anti-inflammation.
I'm Not giving medical advice - Only listing my daily intake.
But eating plant-based foods and avoiding 'junk foods' and processed-foods, sugar, alcohol, smoking, foods high in salt, fried-foods, margerine etc - Is favourable for your digestive system, liver, kidneys, lungs, blood circulation, braincell production and overall wellbeing.
I'm sure this is common knowledge.
Your body functions in 1 of 2 states - 1. Digestion. 2. Healing.
If you are Not Digesting - You Are Healing.
Digestion does Not mean 'Mouth to stomach to rectum'.
Some digestive-processes go on for hours, days and even weeks at the cellular level.
Red meat is reknowned for taking many days to break-down (pineapple speeds this up, slightly).
Basically - If you understand the nutritive pros & cons - you'll be healthier and your body will be a less hospitable environment to unwanted germs.
'Eat To Live, Not 'Live To Eat' is a good philosophy to adopt.
Again - I'm Not Giving advice - Just sharing my own.
Best wishes to All.