SPLIT-VIRUS INFLUENZA VACCINES - DO THEY PROVIDE ADEQUATE IMMUNITY IN THE ELDERLY

Background. Senescence of T-cell function increases susceptibility to influenza with aging. In healthy elderly, we have found that inactivated whole-virus vaccine (WVV) effectively boosts helper T-cell (T-h)-mediated immunity. Recently, however, the use of WVV has been superseded by split-virus vaccine (SVV) to questionably reduce adverse effects of vaccination. Methods. Healthy young adults were compared to healthy elderly adults for their response to SVV. Peripheral blood mononuclear cells (PBMC) obtained pre-vaccination and 6 and 12 weeks post-vaccination, were cultured with live influenza virus, and supernatant IL2 activity was measured. Results. Both groups showed an increase in in vitro IL2 activity by 6 weeks post-vaccination but IL2 decreased to prevaccination levels by 12 weeks. Young and elderly adults who had received WVV one year prior did not respond to SVV in this study. Conclusions. SVV does not provide T-h-mediated immunity for the duration of the flu season and may actually suppress T-h-mediated immunity in previous recipients of WVV.