Nasal and circulating antibody responses to influenza vaccination and their importance in resistance to infection.

Small groups of volunteers were inoculated intranasally with live-attenuated, and parenterally with detergent-split-saline or with whole-virus-oil-adjuvant influenza A2/HK (H3N2) vaccines after the prevalence of Hong Kong strains. Antibody titres in nasal secretions and serum were measured by HI, antineuraminidase and neutralization tests. The oil adjuvant vaccine produced large rises in antibodies and the other two vaccines produced small rises. The volunteers given oil adjuvant and live vaccine were both well protected against challenge with a partly attenuated strain. Statistical analysis showed that resistance to infection was predicted best by high titres of antibody in the serum, but the presence of antibody did not seem to explain completely resistance to infection.