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.
Estamos numa cidade onde mais de 90% da população tem defesas contra o sarampo. Quer dizer que tiveram a doença e geraram defesas naturais. Sobreviveram. Ou receberam a vacina contra o sarampo.