Adverse events occur only rarely after vaccine exposure. Yet, given the high vaccine coverage rates in the United States, the public is increasingly becoming concerned that vaccines may be causing immediate or long-term health problems and less concerned about the possibility of becoming infected. More than 10,000 reports of possible vaccine-related adverse events are reported every year to VAERS, the passive surveillance system that monitors vaccine safety after licensure. As providers of primary health care services to women, midwives are ideally positioned to answer women's questions about vaccine safety. This article provides the background midwives need to be able to help their clients make informed vaccine decisions. It discusses the incidence and risks of infection, the efficacy and risks of vaccines, issues complicating the evaluation of vaccine safety, the state of vaccine safety monitoring systems, and approaches consumers use in vaccine decision making.