In addition, we showed at study entry that previous seasonal flu vaccination (in 2006–2009) did not lead to an increased IFN-γ production in response to flu antigen components from 2006–2009 flu vaccines, but was instead associated with significantly lower IFN-γ production in response
to flu antigen components from 2008–2009 flu vaccines (A/H1N1/Brisbane/59/2007, A/H1N1/Solomon
Islands/3/2006 and B/Florida/4/2006).