Vaccines boost the immune system’s ability to “remember” harmful microorganisms and how to fight them. Normally, it takes roughly a week or two for the immune system to mount an attack against microbes it does not recognize (about as long as it takes to recover from a bad cold). During this time, some of these microorganisms can cause serious health problems. Vaccines contain killed or weakened (attenuated) microorganisms or fragments of bacteria or virus that have been rendered harmless. The immune system eliminates the pathogens from the body and “remembers” them should they invade again. In other words, by triggering a “false” microbial attack, vaccines help the immune system recognize harmful microbes and attack them more quickly if they ever return. For details on recommended vaccines and their benefits and risks, see your health professional.