[1] Univ North Carolina, Dept Pediat, 333 South Columbia St,450 MacNider,CB 7217, Chapel Hill, NC 27599 USA
[2] Univ North Carolina, Dept Pharm, Sch Med, CHAPEL HILL, NC USA
[3] Natl Inst Allergy & Infect Dis, NIH, Epidemiol & Populat Studies Sect, Div Intramural Res, Bethesda, MD USA
[4] Natl Jewish Hlth, Dept Med, Denver, CO USA
[5] Univ Colorado, Dept Med, Aurora, CO USA