[Evaluation of the immunity to A/swine influenza virus in a sample of population of Rome].

Hemagglutination-inhibiting (HI) antibodies in respect of type A/swine influenza virus (strain NIB/3) were titrated on 225 serum specimens taken in Rome during 1976. No HI antibodies to the A/swine virus were found in the serum specimens of the 155 subjects under 50 years of age, while the majority (94%) of the serum specimens of the subjects over 70 years of age showed HI antibody reactivity to the virus, with a mean geometric titre of 21.75. The vaccination of 38 individuals over 50 years of age with live attenuated influenza virus (strain H3N2 - A/Port Chalmers/1/73) failed to cause any elevation of HI antibody titres against A/swine influenza virus, though producing significant seroconversion in respect of the A/Port Chalmers influenza virus in more than 60% of the vaccinees.