Inactivated influenza vaccines can now be made from purified haemagglutinin and neuraminidase. Although they have not been fully tested in the field they probably produce as good an immunity as whole virus vaccines and fewer reactions. They could be used against a new serotype in the face of a pandemic. Revaccination with killed vaccine may be effective, but one careful study in a school during the drifting of the H3N2 showed that it was not effective there overall. Live influenza vaccines have been made that were safe and effective and agreed methods are available for their evaluation. When the new generation of live vaccine strains are available, that have been more fully characterized genetically and functionally, they should be evaluated in substantial long-term field trials.