[1] Ctr Dis Control & Prevent, Natl Ctr Immunizat & Resp, Influenza Div, Atlanta, GA USA
[2] George Washington Univ, Sch Med, Div Pediat Infect Dis, Washington, DC USA
[3] George Washington Univ, Sch Med, Childrens Natl Med Ctr, Div Blood & Marrow Transplantat, Washington, DC USA
[4] George Washington Univ, Sch Med, Dept Pediat, Washington, DC USA
[5] George Washington Univ, Sch Med, Div Microbiol, Div Immunol & Trop Med, Washington, DC USA