[1] Cincinnati Childrens Hosp Med Ctr, Div Biostat & Epidemiol, Cincinnati, OH 45229 USA
[2] Ctr Dis Control & Prevent, Natl Ctr Immunizat & Resp Dis, Atlanta, GA USA
[3] Univ Rochester, Sch Med & Dent, Rochester, NY USA
[4] Vanderbilt Univ, Sch Med, Nashville, TN 37212 USA
[5] Wake Forest Univ, Winston Salem, NC 27109 USA