Figure 1.

 The haemagglutination inhibition (HI) antibody response induced after vaccination and challenge. Groups of 20 mice were vaccinated with two doses of vaccine (12 or 20 μg HA), alone or with aluminium hydroxide adjuvant (60 μg Al). Unimmunised mice served as a control group. Mice were challenged with the highly pathogenic A/chicken/Italy/13474/99 (H7N1) strain 3 weeks after the second dose. Serum HI titres were measured by a modified HI assay using cell grown H7N1 virus and horse red blood cells at 18 days after the second vaccination (pre) and 14 days after challenge (post). The horizontal lines represent the geometric mean titre (GMT), and each symbol represents one animal from the adjuvanted (+) or non‐adjuvanted (−) groups. The limit of detection of the HI assay was eight, and negative titres were assigned a value of four.