Influenza Vaccines for the Elderly

Abstract

The first influenza vaccines were developed approximately 50 years ago by cultivating the virus in hens' eggs and inactivating it with formalin. Since influenza was viewed as a threat to military readiness, for many years thereafter the vaccines were regularly evaluated in randomized, controlled trials among military recruits; the vaccines were consistently found to be safe and at least 70 percent effective in preventing laboratory-confirmed clinical influenza¹. In spite of this good record and the fact that the current vaccine is more potent and has greater purity than the original, its value and appropriate use continue to be debated. . . .