Immunogenicity of a single dose of trivalent influenza vaccine including A/Philippines (H3N2): Results of a field trial

During 1982, a new A(H3N2) influenza virus subtype, A/Philippines/2/82, was identified, and this strain was combined with previous A(H1N1) and B influenza virus strains in the trivalent inactivated vaccine recommended for the 1983-1984 influenza season. Prior to the widescale use of this vaccine in Israel, a group of 106 young male soldiers was vaccinated under controlled conditions. Before vaccination, antibody titers greater than or equal to 1:40 were found in 14.1% against A/Philippines (H3N2), 18.1% against A/England/333/80 (H1N1), and 13.3% against B/Singapore/222/79. Two weeks following vaccination, 78.9% of the vaccinees for whom repeated blood samples were available, had antibody titers in this range for A/Philippines (H3N2), 92.9% for A/England (H1N1), and 80.0% for B/Singapore. The vaccine was only mildly reactogenic, and there were no cases of absence from work following vaccination. Thus the antibody response of young subjects to a single dose of a vaccine containing a new A(H3N2) subtype was found to be satisfactory, and the side effects experienced were minimal.