New developments in influenza vaccine technology: a potential new prevention strategy for employers and managed care organizations.

Influenza is still one of the most wide-reaching, deadly infectious diseases in the United States, with an estimated 54 million cases and 42,000 deaths in a typical year. At $14 billion, the annual cost of influenza is also enormous. More than 80% of that figure comes from so-called indirect medical costs-eg, the productivity loss that results when a person with influenza misses work. The economic cost makes the disease of special concern to employers, who bear the financial burden of such indirect costs, and to the managed care organizations that serve them. Although several therapies moderate the severity of influenza symptoms, prevention remains the best strategy for reducing the disease's morbidity and mortality, as well as the economic cost. Vaccines composed of inactivated (ie, killed) virus have been available for more than 50 years, and with millions of doses now administered, these inactivated vaccines have earned a strong safety record. When the viral strains contained in the vaccine match those circulating, efficacy against serologically defined infection can be as high as 88%. When the match is not good, however, the inactivated vaccine may have substantially lower efficacy. Another shortcoming is that the inactivated virus vaccine requires injection, which can deter compliance in those who have needle phobia or simply dislike getting shots. These concerns have fueled the development and application for licensing of a cold-adapted, live-attenuated influenza virus vaccine (CAIV), which is administered nasally and is not capable of causing disease. Compared with the inactivated vaccine, the CAIV may have superior efficacy and appears to have similarly minor systemic side effects. In addition, CAIV does not require injection and therefore does not cause local pain or tenderness when administered. This article summarizes recent studies of CAIV indicating that it is effective and safe. With its likelihood of enhanced compliance, its ease of administration, and its potentially superior efficacy, CAIV could play a significant role in influenza prevention.