Data collection
C4R is currently collecting information on SARS-CoV-2 infection, COVID-19 illness, and other pandemic-related exposures, across over 50,000 US adults.
An overview of C4R data from before, during, and after the pandemic is provided here, and the C4R Study Design Paper, published in the American Journal of Epidemiology: https://academic.oup.com/aje/article/191/7/1153/6547556.