US measles outbreak raises questions about immunity

Adults in the United States who were vaccinated against measles decades ago may need a new dose. This, according public health experts battling the nation’s largest outbreak since the virus was deemed eliminated in 2000, would depend on when the adults received the shot and their exposure risk.

Up to 10 per cent of the 695 confirmed measles cases in the current outbreak occurred in people who received one or two doses of the vaccine, according to the US Centres for Disease Control and Prevention (CDC).