Author Contributions: Dr Belongia had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Belongia, Waring, Coleman, Meece, Lindstrom, Shay.
Acquisition of data: Vandermause, Lindstrom, Kempf.
Analysis and interpretation of data: Belongia, Irving, Waring, Coleman, Shay.
Drafting of the manuscript: Belongia, Meece, Shay.
Critical revision of the manuscript for important intellectual content: Belongia, Irving, Waring, Coleman, Meece, Vandermause, Lindstrom, Kempf, Shay.
Statistical analysis: Irving, Waring.
Obtained funding: Belongia.
Administrative, technical, or material support: Vandermause, Lindstrom, Shay.
Study supervision: Meece, Kempf.
Financial Disclosures: None reported.
Funding/Support: Funding for this research was provided by a cooperative agreement with the CDC (grant 1 U01 CI000192-01).
Role of the Sponsor: The manuscript was reviewed and approved for submission by the CDC.
Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the CDC.
Additional Contributions: We thank Burney Kieke, MS, Marshfield Clinic Research Foundation, for statistical review (no compensation) and the research coordinators, interviewers, programmer/analysts, core laboratory staff, and administrative support staff at the Marshfield Clinic Research Foundation for their contributions to this project.