The children in a middle school classroom are all exposed to chicken pox one week. Among these students are John, who had chicken pox when he was much younger, and Sara, who has never had chicken pox. Which student do you expect would be less likely to become ill with chicken pox following this exposure and why? John: he has naturally acquired active immunity to chicken pox from his previous exposure. Sara: she has naturally acquired passive immunity to chicken pox from exposure to other students. John: the pathogens that cause chicken pox will no longer be able to enter his body. Sara: since she has not suffered from chicken pox, her immune system is probably stronger than John’s.