Are there safe herbal supplements that can boost my immune system and prevent bacterial infections?

None which work: Many popular supplements claim to boost the immune system. However scientific testing does not show they they actually work in people eating balanced diet. Oddly enough, taking too much of some supplements can actually weaken the immune system (ex. Zinc) washing your hands, eating well, exercising regularly and getting plenty of sleep is the best way to boost your immune system.

Herbs for immunity: Your ability to fight off bacterial infection is the result of a complex immune system. It is very unlikely that supplementation with herbs could have much impact. The best way to prevent infections is with vaccinations and avoidance of exposures to infectious diseases through hygenic behaviors such as handwashing. Saline nasal washes may be beneficial. Probiotics are being studied currently.