Criteria in the evaluation of live intranasal influenza virus vaccines.

Live influenza virus vaccines should meet the following criteria: attenuation, immunogenicity, lack of spread, genetic stability, production in a suitable cell substrate, and stability during storage. In addition, they should be able to induce a wide antigenic protection. These various aspects will be discussed with reference to the "Alice" strain of live influenza A virus, which possesses all the properties for a good live attenuated virus vaccine.