The immunization schedule is studied extensively and is the best defense against infections that may have serious complications including pneumonia, meningitis, cancer, and even death. The Vaccine Safety Datalink (VSD), the Advisory Committee on Immunization Practices, and the Institute of Medicine have all studied and approved the current immunization schedule. The Centers for Disease Control and Prevention (CDC) immunization schedule, which recommends specific immunizations be given during specific time periods, has been developed to provide the best immune response and protection.