[Recent progress in live influenza vaccine development]

As live influenza vaccine, cold-adapted influenza virus vaccines (ca vaccine) have been extensively investigated in both the U.S and Russia. In Russia it has been licensed since 1988 and it is going to be licensed in the U.S. within a year or two. In general, the ca vaccine is more effective in seronegative population than the inactivated vaccine. In seropositive adult population, both are equally effective. In the elderly, inactivated vaccine is better than the live vaccine. In Japan, clinical trials were also conducted with the American ca vaccines. Although the efficacy was confirmed in limited locations, the vaccine could not be evaluated from the point of license approval because big epidemic did not occur during the studies.