Private vs Govt Vaccine.. Confusion?? What are vaccines? Vaccines are products that are usually given in childhood to protect against serious, often deadly diseases. By stimulating your body’s natural defenses, they prepare your body to fight the disease faster and more effectively. How do vaccines work? Vaccines help your immune system fight infections more efficiently by sparking your immune response to specific diseases. Then, if the virus or bacteria ever invades your body in the future, you