How to cure constant level of low immunity?

Live healthy life.: Eat healthfully w at least 5 servings of vegetables & 4 of fruit /day (organic is best). Increase nutritional fiber. Avoid refined sugar & junk carbohydrates. Avoid sweetened juices, soda & caffeinated beverages. Watch portion sizes. No tobacco, illicit drugs & low to no alcohol use. Aim for 7.5 to 8 hrs sleep /night. Hydrate w at least 64 oz of water / day. Maintain good hygiene. Daily physical