Nothing has improved disease control as thoroughly as immunizations. In well-immunized populations, there is no flaccid paralysis (polio), almost no epiglottitis or postmeningitis deafness (Haemophilus influenzae), and little postviral male sterility (mumps). Immunizations are not perfect; they may cause side effects, some of which have led to the discontinuation of the vaccine when side effects have outweighed the vaccine’s protective effects. However, immunization works best not by the protection it provides the individual but by the protection provided to the population at risk. This article discusses the currently available vaccines along with recommendations for their use.