COMIC CON IS ON!:
Costumed characters pose outside of the convention center on day 1 of the 2014 Comic-Con International Convention held Thursday, July 24 in San Diego. Photo: Associated Press/Denis Poroy/Invision
The vast majority of U.S. kindergarten-age children are vaccinated against preventable diseases but sizable pockets of unprotected children still exist, posing a public health threat, according to a government study.