Influenza Antibodies, Part B With its ability to reassort in animal hosts like pigs and birds, and to cause pandemics, influenza A viruses are often in the spotlight. However, a substantial portion of the annual flu burden is also the result of influenza B virus, which is a single influenza type that is characterized by two antigenically and genetically distinct lineages. Dreyfus et al. (p. 1343 , published online 9 August) identify three monoclonal human antibodies that are able to protect against lethal infection with both lineages of influenza B virus in mice. Two antibodies, which bind to distinct regions of the viral hemagluttinin (HA) molecule, neutralize multiple strains from both lineages of influenza B virus, whereas the third antibody binds to the stem region of HA and is able to neutralize both influenza A and B strains. The structural data from these antibodies bound to HA, together with already known antibodies targeting influenza A, may provide clues for designing a universal vaccine to protect against both influenza virus types.