[1] Ctr Dis Control & Prevent, Natl Ctr Immunizat & Resp Dis, Atlanta, GA 30333 USA
[2] Vanderbilt Univ Sch Med, VICTR, Nashville, TN USA
[3] Univ Rochester Sch Med & Dent, Dept Pediat, Rochester, NY USA
[4] Vanderbilt Univ Sch Med, Dept Pediat, Nashville, TN USA
[5] Cincinnati Childrens Hosp Med Ctr, Dept Pediat, Cincinnati, OH USA