Figure 7.

 Titers of hemagglutination inhibition (HI) antibodies against the novel H1N1 influenza A strains. Mice were immunized with HAC1 twice, at days 0 and 21, and serum samples were collected prior to each immunization, as well as 10 and 21 days after the second dose (study days 31 and 42, respectively). The HAC1 antigen was administered to mice either in the presence of Quil A (s.c.) or adsorbed to Alhydrogel (i.m.). Anti‐A/California/07/09 and A/Texas/5/09 HI antibody titers were expressed as the reciprocal of the highest dilution of serum that inhibits hemagglutination of eight hemagglutinin units of each virus. Samples without detectable HI titers were assigned a titer of 10. Data shown are the mean titers (log₂) from each group of immunized mice ± SE.