The concept of maternal immunization to prevent infectious diseases during a period of increased vulnerability in the infant is supported by historical experience and carefully conducted studies of various viral and bacterial vaccines. Candidate vaccines should be minimally reactogenic, immunogenic, and safe. Health education and access to immunization should be a priority if maternal immunization is to succeed as a disease prevention strategy. The potential effect on the incidence of disease in the newborn and young infant can only increase as more candidate vaccines that could be administered during pregnancy become available. In the future, common infections and other, more dreaded diseases, such as herpes simplex virus infection, cytomegalovirus, and human immunodeficiency virus infection, could be prevented with this intervention. Further research on the safety and efficacy of maternal immunization must continue if the occurrence of serious infectious diseases in neonates and young infants is to be reduced.