Heat Stability of a New 17D Yellow Fever Vaccine

Abstract

For more than 50 years, 17D yellow fever vaccines have largely proven to be well tolerated and effective, justifying their recommendations by WHO for the control of yellow fever. Indeed, the quality and the long duration of protection make this vaccine highly effective provided that it contains a sufficient viral amount, 1000 LD50 (mice)/dose. The well-known heat sensitivity of classical vaccines, resulting in a rapid loss of the viral titer, constituted a major handicap for its use in endemic areas, as it caused failures of immunization when stored at incorrect temperatures. With this in mind, the development of heat-stable vaccine was considered a priority. Different chemicals were systematically assessed at various concentrations and associations for their protective effect on the virus. A stabilizing medium was consequently defined by Barme and Bronnert [1]. During the preparation procedure of the vaccine, it is added to the viral suspension at the time of freeze drying. An overview of the results of different studies of heat stability and immunogenicity of this new 17D thermostable vaccine is presented.