Influenza virus is a serious pathogen that burdens society with health care costs, and can lead to fatality. The virus is dealt with currently by vaccination and anti-influenza drugs. However, vaccines need to be improved towards safer and more efficient production formats, and drugs need to be constantly renewed to cope with resistances. That the neuraminidase inhibitors are only drugs currently available warrants urgent attention to an alternative anti-influenza target. In this paper we introduce studies on fusion activity of influenza virus hemagglutinin (HA), and discuss how to best utilize the knowledge for an improved vaccine development and an anti-influenza drug search. Potential application of mutations resulting in changes in fusion activity to cell culture optimized vaccine virus development and strategies to develop broad spectrum anti-influenza drugs through targeting the conserved fusion domain of the HA are discussed.