[1] Univ Pittsburgh, Dept Family Med & Clin Epidemiol, Sch Med, Pittsburgh, PA 15261 USA
[2] Univ Pittsburgh, Sch Med, Dept Radiat Oncol, Pittsburgh, PA 15261 USA
[3] Univ Pittsburgh, Grad Sch Publ Hlth, Dept Hlth Policy & Management, Pittsburgh, PA 15261 USA
[4] Univ Pittsburgh, Grad Sch Publ Hlth, Dept Behav & Community Hlth Sci, Pittsburgh, PA 15261 USA
[5] Univ Pittsburgh, Med Ctr, Dept Employee Hlth Serv, Pittsburgh, PA 15261 USA
[6] Natl Ctr Immunizat & Resp Dis, Ctr Dis Control & Prevent, Atlanta, GA USA