The S antibody response to vaccination with influenza vaccines containing an Asian strain was evaluated in young adult males over a period of 56 days. Two of the vaccines were aqueous monotypic preparations, and the third was of the polyvalent adjuvant type. With the aqueous vaccines the highest levels of S antibody were attained in about 10 days. A somewhat different response was seen with the adjuvant vaccine. Four-fold titer increases occurred in the first 10 days after vaccination but there was also evidence of further, although slight, titer increases thereafter. Differences were noted between the two aqueous vaccines, one engendering about half of the soluble antibody elicited by the other. These patterns of S antibody response suggest that useful distinctions may be made in the serodiagnosis of influenza in vaccinated populations.
Studies of the hemagglutination-inhibiting antibody response to the adjuvant vaccine disclosed that 9 of 25 men had a minimal and equivocal response as measured by an A2/Japan/305/57 antigen. In 16 of the 25 men, the response occurred more promptly and was of much greater magnitude. Such a distinction was not apparent when the A1/Albany/1/55 virus was utilized to make an otherwise comparable antigen. These differences suggest that prior experience may affect the antibody response to adjuvant vaccines.