1. Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, California, USA
2. Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
3. GlaxoSmithKline, Wavre, Belgium
4. Kaiser Permanente Bernard J. Tyson School of Medicine, Pasadena, California, USA
5. GlaxoSmithKline, Rockville, Maryland, USA
6. GlaxoSmithKline, Rixensart, Belgium
7. GlaxoSmithKline, Siena, Italy