evidence: "The likelihood of a serious adverse event happening because of a vaccine is extremely low. It’s about one in a million, less than the likelihood of getting killed by lightning," Hotez said. A child who hasn’t received the measles, mumps, rubella vaccine is 35 times more likely to contract measles than a vaccinated child in the U.S., and 90 percent of unvaccinated people who come into contact with an infected person will catch the disease. Two doses of the MMR vaccine are 97 percent effective at preventing measles. Rising exemption rates threaten more than just the unvaccinated. The mumps can still infect vaccinated people—as seen with a massive outbreak in 2006, which infected over 6,500 people in the Midwest, despite high vaccination rates. These unimmunized pockets put America at risk, but they’re also a worldwide issue. Non-immunized pockets are a major global issue The U.S. ranks high globally when it comes to vaccination rates, but there is still some variation between states.