▁children . ▁ ▁The ▁concept ▁of ▁v acc ine ▁over load ▁is ▁fla wed ▁on ▁several ▁levels . ▁Despite ▁the ▁increase ▁in ▁the ▁number ▁of ▁v acc ines ▁over ▁recent ▁dec ades , ▁improvements ▁in ▁v acc ine ▁design ▁have ▁reduced ▁the ▁imm un olog ic ▁load ▁from ▁v acc ines ; ▁the ▁total ▁number ▁of ▁imm un ological ▁components ▁in ▁the ▁ 1 4 ▁v acc ines ▁admin ister ed ▁to ▁US ▁children ▁in ▁ 2 0 0 9 ▁is ▁less ▁than ▁ 1 0 % ▁of ▁what ▁it ▁was ▁in ▁the ▁ 7 ▁v acc ines ▁given ▁in ▁ 1 9 8 0 . ▁A ▁study ▁published ▁in ▁ 2 0 1 3 ▁found ▁no ▁correlation ▁between ▁aut ism ▁and ▁the ▁ant igen ▁number ▁in ▁the ▁v acc ines ▁the ▁children ▁were ▁admin ister ed ▁up ▁to ▁the ▁age ▁of ▁two . ▁Of ▁the ▁ 1 , 0 0 8 ▁children ▁in ▁the ▁study , ▁one ▁quarter ▁of ▁those ▁diagn osed ▁with ▁aut ism ▁were ▁born ▁between ▁ 1 9 9 4 ▁and ▁ 1 9 9 9 , ▁when ▁the ▁routine ▁v acc ine ▁schedule ▁could ▁contain ▁more ▁than ▁ 3 , 0 0 0 ▁ant ig ens ▁( in ▁a ▁single ▁shot ▁of ▁D TP ▁v acc ine ). ▁The ▁v acc ine ▁schedule ▁in ▁ 2 0 1 2 ▁contains ▁several ▁more ▁v acc ines , ▁but ▁the ▁number ▁of ▁ant ig ens ▁the ▁child ▁is ▁exposed ▁to ▁by ▁the ▁age ▁of ▁two ▁is ▁ 3 1 5