The humoral immune response and protective efficacy of vaccination with inactivated split and whole influenza virus vaccines in BALB/c mice

Recently the urgency of developing a pandemic influenza vaccine has lead to the re-evaluation of the use of whole virus vaccine. We have compared the humoral immune response and the protective efficacy of whole and split influenza virus vaccines in mice. Whole virus vaccine was more immunogenic particularly after the first dose of vaccine, generally eliciting higher numbers of systemic antibody secreting cells and an earlier and higher neutralising antibody response. Immunisation with one dose of whole virus vaccine more effectively reduced viral shedding upon non-lethal homologous viral challenge, but two doses of split virus vaccine was most effective at limiting viral replication and this was correlated with high influenza specific serum IgG concentrations. The two vaccine formulations induced different T helper profiles particularly after one dose of vaccine; split virus vaccine induced a type 2 bias response, whereas whole virus vaccine elicited a dominant type I response. (c) 2006 Elsevier Ltd. All rights reserved.