COLD-ADAPTED LIVE ATTENUATED INFLUENZA VACCINES DEVELOPED IN RUSSIA -CAN THEY CONTRIBUTE TO MEETING THE NEEDS FOR INFLUENZA CONTROL IN OTHER COUNTRIES

It is now more than 30 years since the first cold-adapted influenza vi ruses were developed in Russia as potential live, attenuated vaccines. In the past 15-20 years considerable experience has been gained from Russian and joint Russian-US laboratory and clinical studies with type A monovalent and bivalent vaccines prepared with genetic reassortant viruses derived from one of these cold-adapted viruses in particular, A/Leningrad/134/57. More recent experiences include use of trivalent c old-adapted vaccines with a type B component. The overall high level o f safety of individual and combined vaccines in pre-school and school- aged children, with illness reductions in open field trials equivalent to that seen with inactivated vaccines, is such as to suggest that pr actical measures might now be justified to facilitate expansion of the use of these vaccines to other countries. It is proposed that further experimentation with the Russian cold-adapted live attenuated vaccine s should be focused on issues that will relate to the public health pe rspective, i.e. selection of the single best candidiate type A and B v accines for intense study using as criteria their potential for meetin g licensing requirements outside Russia, and documenting the clinical protective efficacy of a single vaccine dose compared to two doses as studied until now. Resolution of these issues is important to ensure t hat costs for future live vaccine production, control, and utilization will be kept at lowest levels so that expanded use of live vaccines w ill have maximum cost-benefit and affordability. To guide those intere sted in these issues, examples are given of populations for whom a lic ensed live cold-adapted vaccine might be considered, together with ind ications of extra data needed to fully validate each suggested use.