This is the equivalent of "roll your own encryption" in the computer security world.
The number of real world cases where people have no or little immune system is likely minuscule (real numbers?) compared to the number of people that destroy their immune system through poor life and health choices. (obviously high number)
Eat better, exercise some (any?) and let your immune system take care of this stuff. That is what it's there for. Introducing _another_ foreign substance that will need to be fought off later is a recipe for disaster.