In addition , less than half of school-age children -- the population mainly responsible for spreading the flu virus -- got the flu shot , experts said . The flu vaccine showed 80 % effectiveness among those 65 and older , CDC says . The vaccine was about 56 % effective in adults and children , it says . New studies show that rates are low in most populations .
The flu vaccine showed 80 % effectiveness among those 65 and older , CDC says . The vaccine was about 56 % effective in adults and children , it says . New studies show that rates are low in most populations .