The quadrivalent inactivated influenza vaccine is targeted against currently circulating H1N1 and H3N2 influenza A viruses, and Yamagata and Victoria lineage influenza B viruses (4 circulating types of virus = 4 components of the vaccine). Universal vaccine approaches (as we’ve mentioned in responses to other questions in this session) are hoping to expand vaccine breadth not by including more individual HA targets, but by targeting conserved parts of the virus that are consistent across a wide range of virus subtypes.