Daily experience will show that the immunity of the newborn is different from that of older children and adults. Certain types of infection follow a strikingly severe and others a strikingly mild course, or there may be complete lack of susceptibility. To some extent this divergent pattern may be explained by factors not connected with the immunity of the newborn infant. Intrauterine infection is different from that ordinarily encountered in pathway of entry and also often in degree. But otherwise it is essentially the specific immunity of the host that brings about the divergent course.
The immunity of the newborn infant is determined by two entirely different factors: (1) the active immunity mechanisms of the infant itself, and (2) the passive protection conferred by the mother. Essentially, the formar is the same, in each infant, and is not affected by the time and place of birth. The latter, however, varies