Mumps outbreak in Borough Park, NY

City health officials warned Thursday of an outbreak of the old-fashioned childhood disease mumps in the Borough Park section of Brooklyn.
The outbreak was traced to a child who went to Britain - where the illness is more common because of lower levels of vaccination - and then attended a summer camp upstate, apparently infecting dozens of kids.
City health officials say there are 57 confirmed or probable cases and they are investigating more. Those infected are mostly between 10 and 15 years old.
Puzzlingly, 75% of the victims had the normal two doses of mumps vaccine, which is supposed to protect against the illness 90% of the time.