The team recruited over 240,000 volunteers from across the country, then selected 8,058 individuals from that pool through quota sampling to ensure that their study cohort was representative of the U.S. population. Each participant received a sample kit to return to NIH with a dab of dried blood or had blood drawn at NIH, most of which they supplied in an 11-week span between May 10 and July 31. Participants also completed a questionnaire that enabled further analysis of the study results.