FACTORS AFFECTING THE YIELD OF COLD-ADAPTED INFLUENZA-VIRUS VACCINE

Various manipulations to production procedures have been investigated in order to discover methods to attain adequate or augmented titers of cold-adapted influenza virus (CAIV) vaccine. The methods modified inc lude those used for reassortant selection and the determination of vir us growth parameters. Increased: infectivity titers were achieved thro ugh selection of high-yielding mutants by isolating multiple plaques d uring plaque purification of reassortant clones, as well as through op timiztion of egg incubation times, age, and lot for individual strains . Up to 6-fold increases in virus yield were obtained by selecting hig h yielding mutants, up to 9-fold increases were achieved by modifying egg incubation times, and a nearly 1 log increase was realized by dete rmining the ideal egg age for individual strains. (C) 1997 Elsevier Sc ience B.V.