Thanks to vaccinations, measles was declared eliminated in the United States in 2000. But measles cases are now back, and one big reason is that, across the country, more families have exempted their children from routine immunizations than ever before. CBS News chief medical correspondent Dr. Jon LaPook looks at how the views of “anti-vaxxers” are precipitating new health crises; and talks with health experts about the dangers posed by anti-vaccine and anti-science movements.