Studies with live attenuated influenza vaccines

Inhibitor-resistant and temperature-sensitive live attenuated influenza virus vaccines were administered to normal volunteers and elderly and chronically ill persons to assess safety, antigenicity, and transmissibility. Recombinants of both types of vaccine were made using currently prevalent influenza virus strains (A/Hong Kong/68, A/England/42/72, A/Scotland/74, A/Victoria/75) over a five-year period to keep the vaccine relevant with regard to antigenic drift. The results indicate that both vaccine types are safe, antigenic and non-transmissible and that for both types of vaccines, recombinants can be made to new antigenic drifts. The inhibitor-resistant vaccine replicates to lower titers in the nasopharynx than the temperature-sensitive virus, and this is considered an advantage, whereas the genetic defect of the temperature-sensitive virus is better defined than that of the inhibitor-resistant vaccine.