[1] Harvard Univ, Sch Publ Hlth, Ctr Biostat AIDS Res, SDAC, Boston, MA 02115 USA
[2] Univ Sydney, NHMRC, Clin Trials Ctr, Sydney, NSW 2006, Australia
[3] Univ Calif San Diego, San Diego, CA 92103 USA
[4] San Diego Vet Affairs Healthcare Syst, San Diego, CA USA