It is an object of the present invention to provide an extract from inflamed skins of rabbits inoculated with vaccinia virus wherein the quality is more stabilized, and a preparation containing the extract, etc. The use of the amount of N-acetylneuraminic acid contained in an extract from inflamed skins of rabbits inoculated with vaccinia virus and a preparation containing the extract as an index makes possible to warrant the quality of each manufacturing lot of the extract and the preparation in more stable manner. The extract from inflamed skins of rabbits inoculated with vaccinia virus and the preparation containing the extract which are manufactured as above, and in which the quality thereof becomes more stable, are warranted to maintain efficacy and safety in more strict manner, and thus extremely useful.
