We are in a city where more than 90 percent of the population has defenses against the measles, which means that they either had the disease, survived, and developed natural defenses; or that they had been immunized against measles.
우리가 사는 도시에 90퍼센트 이상의 사람들이 홍역에 대한 면역력이 있는데 병을 앓았다가 나아서  자연 면역력이 있거나 홍역 접종을 받은 겁니다.