Influenza vaccine

摘要

A strain of influenza virus, especially human influenza type A or B, for use in formulating a vaccine is selected by a process which comprises isolating candidate influenza viruses in embryonated hens' eggs, determining whether they have antigenic similarities to strains which are the same except that they have been isolated and grown exclusively in animal cells, that is to say whether they are "cell-like", and selecting at least one such cell-like strain or a reassortant thereof having its HA and NA genes for the vaccine.