Author Contributions: Dr Zhou 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: Zhou, Harpaz, Jumaan,
Acquisition of data: Zhou.
Analysis and interpretation of data: Zhou,
Harpaz, Jumaan, Winston.
Drafting of the manuscript: Zhou, Harpaz, Jumaan.
Critical revision of the manuscript for important
intellectual content: Zhou, Harpaz, Jumaan, Winston, Shefer.
Statistical analysis: Zhou, Winston.
Administrative, technical, or material support:
Harpaz, Jumaan, Shefer.
Study supervision: Jumaan.
Financial Disclosures: None reported.
Disclaimer: The findings and conclusions in
this report are those of the authors and do not necessarily represent the
views of the Centers for Disease Control and Prevention, US Department of
Health and Human Services.
Acknowledgment: We thank the following individuals
from the Centers for Disease Control and Prevention: Jane Seward, MBBS, MPH,
and Dalya Guris, MD, MPH, for their thoughtful reviews of an early version
of the manuscript; and Mary McCauley, MTSC, for her editorial assistance.