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Changes in HI and VN titers against H1N1 influenza viruses isolated from 1989 to 2008 in representative V-IH lots manufactured from 1999 to 2008.
Notes: Antibody titers against vaccine strains (A and B). Antibody titers against clinical isolates (C and D). Closed circle: HI titer; closed square: VN titer.
Abbreviations: HI, hemagglutination inhibition; VN, virus neutralizing; V-IH, Venoglobulin IH.
