原文：
Vaccines are one of the most effective tools we have to prevent disease and death in both individuals and populations. Vaccines work by stimulating the immune system to recognize and respond to specific pathogens, such as viruses or bacteria, by producing an immune response that can neutralize or eliminate the pathogen. This immune response also leaves the body with a memory of the pathogen, which enables the immune system to respond more quickly and effectively in the event of future exposure.

重述：
Vaccines are highly efficient in the fight against diseases and mortality, both individually and at large. They activate the immune system to detect and combat specific pathogens like viruses and bacteria. This triggers the production of an immune response capable of neutralizing or eliminating the pathogen. Additionally, the immune system retains a memory of the pathogen, resulting in a faster and more effective response in case of future exposure.