Trivalent split or subunit influenza vaccines [A/Shangai/11/87 (H3N2), A/Singapore/6/86 (H1N1) and B/Yamagata/16/88] recommended for the 1989-90 winter season and licensed in Italy, were administered to 149 volunteers of three different age groups (elderly, middle-aged and young). Antibody production was determined in pre- and postvaccination sera by haemagglutinin inhibition test and the results were evaluated as protection and response rates. The split vaccine was more immunogenic than the subunit preparation, especially against the B virus strain. Age had no obvious impact on the degree of responsiveness to vaccination. © 1991.
Zei, T., Neri, M., & Iorio, A. M. (1991). Immunogenicity of trivalent subunit and split influenza vaccines (1989-90 winter season) in volunteers of different groups of age. Vaccine, 9(9), 613–617. https://doi.org/10.1016/0264-410X(91)90184-8