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.
Мы в городе, где более 90% населения защищены от кори. Это означает, что они переболели и выработали иммунитет — выжили или были привиты против кори.