Antibody response to inactivated influenza vaccines of various antigenic concentrations.

Four inactivated influenza vaccines (containing the recommended antigens for the 1985-1986 influenza season) of various antigenic concentration levels were randomly administered to 140 study participants. The effect of the increasing antigen concentration resulted in significantly higher influenza hemagglutination inhibition (HI) antibody levels 3 weeks after vaccination for the A/H1N1 antigen but not for the A/H3N2 or B antigens. Also, at 3 weeks after vaccination, there were significantly lower antibody titer levels associated with increasing age for the A/H1N1 and B antigens (adjusting for the prevaccination antibody titer and antigen content).