Split-virus influenza vaccines: do they provide adequate immunity in the elderly?

Abstract

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 (Th)-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 Recently, however, the use of WVV has been superseded by split-virus vaccine (SVV) to questionably reduce adverse effects of vaccination.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 pre-vaccination 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 Th-mediated immunity for the duration of the flu season and may actually suppress Th-mediated immunity in previous recipients of WVV.