Figure 5
The cross-HI reactions between the F/98 and rF/HAA180V viruses. Three-week-old SPF chickens were vaccinated one time with a subcutaneous injection of 0.3 mL of oil-emulsion of the inactivated whole virus vaccines of the F/98 and rF/HAA180V viruses, which were inactivated by adding 0.2% formalin (v/v) for 24 h at 37 °C. At 21 days post-vaccination, 12 chickens from each group (the F/98 and rF/HAA180V vaccine groups) were bled to analyse cross-HI titres against the F/98 and rF/HAA180V viruses. Statistical significance was based on Student’s t test (*P < 0.05).