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.
この街では 人口の90%以上が麻疹への抗体があり― つまり 既に一度麻疹に罹り自然に抗体が出来ているか 麻疹ワクチンを打っているか どちらかです