The potential advantages and requirements of live attenuated influenza virus vaccines

Live attenuated influenza A virus vaccines are potentially the most efficient and effective method of immunization against epidemic influenza, and offer the only feasible means of mass vaccination at a socially acceptable cost. The advantage of live virus vaccines are described and compared with killed virus vaccines in terms of immune responses, protection and commercial production. The most frequently considered methods of attenuation and their individual drawbacks are discussed with speculation on the future development and rationale of master vaccine strains. Recommended minimal requirements of master vaccine strains and candidate live vaccines are presented as a basis for their eventual evaluation by licensing authorities.