The discovery of vaccines has led to the near eradication of several important diseases and has had a tremendous impact on health for a relatively low cost. However, most vaccines in use today were developed by techniques that were pioneered more than 100 years ago and do not represent the full potential of the field. The introduction of genetic engineering has fueled rapid advances in vaccine technology and is now leading to the entry of new products in the marketplace.In the past, options for the utilization of vaccines in the area of managed care had been quite limited because of the historically straightforward application of immunizations. The growing number and type of vaccine targets, coupled with novel, more effective formulations, adjuvants, and routes of delivery for vaccines, will undoubtedly create new challenges. Although progress in vaccine technology has the potential to prevent illness and reduce the economic burden of diseases in the long term, thereby improving outcomes, ongoing problems remain in the short term.Who should and will pay for these anticipated improvements in health?How will this period of change be managed?This article describes the present "vaccine revolution" and attempts to answer these questions, which are becoming increasingly important in managed care.