Jane rides the crowded train to work taking orders at subway. Bill works alone at home. Jane gets a lot of colds Bill doesn't. Does bill have a better immune system? After 30 head colds over 4 years, Jane has a variety of antibodies to rhinoviruses. She doesn't get sick as often as the new hire. Does she have have a better immune system? Or a normal immune system with more training? Asthmatic smoker Jim gets COVID and dies. Healthy Joe gets it and is under the weather for four days. Is that the immune systems fault for Jim?