It’s cold and flu season, and most of us will encounter a virus at some point. So, how does our immune system work to keep us healthy? According to Michaela Gack, PhD, Scientific Director of the Cleveland Clinic Florida Research and Innovation Center, once we fight off a virus, our immune system does its best to protect us from a second infection. “Whenever we have a second infection, these antibodies can be produced and thereby protect us but there are some limitations,” said Dr. Gack. “It only works if it’s the same virus or very similar virus.”