When children are small they are given vaccines that are usually dead viruses given to the body. These viruses don't cause damage to body and the body takes it as a real virus and prepare antibodies in the body but when a certain real disease or virus is in the body , the already presented antibodies fight with them for the protection of the body. These antibodies remain in the body so that when a disease or virus attacks the body the antibodies are already geared up to fight against them. Thus antibodies protect the body against invading microbes or viruses.
