Learn about the concept of herd immunity in this video from NOVA: "Vaccines—Calling the Shots." Vaccinations protect communities, not just individuals, as illustrated by the 2013 measles outbreak in Brooklyn, New York. Because a significant portion of the population (95 percent) was vaccinated against measles, the disease was prevented from spreading to the rest of the city. In contrast, in France, where the vaccination rate was 89 percent and the herd immunity was compromised, the disease had a much greater impact. There were 15,000 cases of measles in France in 2011.