The protective immunity induced by influenza vaccinations is mediated primarily by antibodies that recognize the viral haemagglutinin protein and neutralize virus infectivity. After virus infection, host innate immune responses, including production of cytokines and chemokines, are activated which initiate a cascade of immunological events that lead to the development of specific immune responses to the virus. Controlling and clearing influenza virus infection requires neutralizing antibodies and cell-mediated immunity (for example, activation of T cells) [3] . The influx of immune cells into an influenza-infected lung can lead to the overproduction of various cytokines and chemokines -often called a 'cytokine storm' -which can enhance the virus-induced lung damage resulting in severe illness. A limited number of studies suggest that an altered cytokine and chemokine response is contributing to severe 2009 H1N1 disease [8, 9] . Therefore, immunity to influenza viruses represents a balance between immune responses inducing protection and clearance of virus versus causing pathology.