Influenza at Christ's Hospital: March, 1974.

Boys in a boarding-school given inactivated influenza-A or influenza-B vaccine have been observed during a simultaneous outbreak of influenza due to A/Port Chalmers, B/Hong Kong, and B/Intermediate strains. Influenza-B vaccine conferred substantial protection, the attack-rates in boys given B vaccine being 24% compared with 45% in a control group. A/Hong Kong vaccine, by preventing infection during the previous influenza A/England outbreak, left the boys vulnerable to influenza A/Port Chalmers. Influenza-A haemagglutination-inhibiting (H.I.) antibody acquired by natural infection was associated with more protection than H.I. antibody induced by vaccination. This difference was not seen with influenza-B H.I. antibody.