[1] Univ Colorado, Adult & Child Consortium Hlth Outcomes Res & Deli, Anschutz Med Campus,13123 East 16th Ave,Box 055, Aurora, CO 80045 USA
[2] Childrens Hosp Colorado, 13123 East 16th Ave,Box 055, Aurora, CO 80045 USA
[3] Univ Colorado, Dept Pediat, Anschutz Med Campus, Aurora, CO USA
[4] Ctr Dis Control & Prevent, Natl Ctr Immunizat & Resp Dis, Atlanta, GA USA
[5] Denver Hlth, Div Gen Internal Med, Denver, CO USA
[6] Univ Colorado, Colorado Sch Publ Hlth, Dept Community & Behav Hlth, Anschutz Med Campus, Aurora, CO USA