[1] Ctr Dis Control & Prevent, Influenza Div, Atlanta, GA 30333 USA
[2] Mayo Clin, Coll Med, Mayo Vaccine Res Grp, Program Translat Immunovirol & Biodefense, Rochester, MN USA
[3] Mayo Clin, Coll Med, Dept Internal Med, Program Translat Immunovirol & Biodefense, Rochester, MN USA