[Serological studies of influenza viruses in a sample of the population of Rome].

Haemagglutination inhibiting antibodies (H.I.A.) to influenza viruses A/Victoria/3/75, A/Victoria/112/76, B/Hong Kong/8/73 and A/New Jersey/8/76 were titrated in 1110 serum specimens collected in Rome in the period between March-May 1977 and obtained from subjects 0-60 years old. The H.I.A. protective level (greater than or equal to 1 : 40) found in 21.7% of the sera against A/Victoria/3/75 is such that it does not avoid a possible diffusion of this strain in the successive epidemic season. Moreover this finding suggests that there will be probably no antigenic change (4) in the same period. The age group 0-20 showed the higher titer H.I.A. Low protective levels were found against the virus A/Victoria/112/76 and B/Hong Kong/8/73, while the H.I.A. to virus A/New Jersey/8/76 showed a percentage of protective level increasing with the age.