The Mother Asks the Nurse Why Her Child Must Have

The mother asks the nurse why her child must have three doses of a certain vaccine over the next few months.The nurse would correctly educate the mother by stating:

A) "The drug level must be high enough to prevent disease."
B) "For some diseases, multiple doses are needed over time to allow the development of full immunity."
C) "It is prophylactic because not all parents get the immunizations at the correct time."
D) "We are not certain, but more doses have proved more effective."