Serum antibody response in mice after administration with inactivated vaccines.

Four-week-old BALB/c mice (12 heads per group) were immunized with inactivated whole-virus a-Brisbane/59/07, a-CAN01/04 and RgCA/04/09xPR8 vaccines containing 1.77 or 3.5 µg of HA administered once or twice with aluminum hydroxide adjuvant. Serum samples were collected 2 weeks after the last vaccination. The limit of detection for the HI assays done was set to <20 HI units and HI titers are expressed as the reciprocal of the highest dilution of serum that inhibits 8 HA units of virus (e.g., as 80 versus 1∶80).