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Nash, Denis; Rane, Madhura; Chang, Mindy; Kulkarni, Sarah Gorrell; Zimba, Rebecca; You, William; Berry, Amanda; Mirzayi, Chloe; Kochhar, Shivani; & Maroko, Andrew, et al. (Preprint). SARS-Cov-2 Incidence and Risk Factors in a National, Community-Based Prospective Cohort of U.S. Adults. medRxiv. PMCID: PMC7899475


BACKGROUND: Epidemiologic risk factors for incident SARS-CoV-2 infection as determined via prospective cohort studies greatly augment and complement information from case-based surveillance and cross-sectional seroprevalence surveys.
METHODS: We estimated the incidence of SARS-CoV-2 infection and risk factors in a well-characterized, national prospective cohort of 6,738 U.S. adults, enrolled March-August 2020, a subset of whom (n=4,510) underwent repeat serologic testing between May 2020 and January 2021. We examined the crude associations of sociodemographic factors, epidemiologic risk factors, and county-level community transmission with the incidence of seroconversion. In multivariable Poisson models we examined the association of social distancing and a composite score of several epidemiologic risk factors with the rate of seroconversion.
FINDINGS: Among the 4,510 individuals with at least one serologic test, 323 (7.3%, 95% confidence interval [CI] 6.5%-8.1%) seroconverted by January 2021. Among 3,422 participants seronegative in May-September 2020 and tested during November 2020-January 2021, we observed 161 seroconversions over 1,646 person-years of follow-up (incidence rate of 9.8 per 100 person-years [95%CI 8.3-11.5]). In adjusted models, participants who reported always or sometimes social distancing with people they knew (IRR(always vs. never) 0.43, 95%CI 0.21-1.0; IRR(sometimes vs. never) 0.47, 95%CI 0.22-1.2) and people they did not know (IRR(always vs. never) 0.64, 95%CI 0.39-1.1; IRR(sometimes vs. never) 0.60, 95%CI 0.38-0.97) had lower rates of seroconversion. The rate of seroconversion increased across tertiles of the composite score of epidemiologic risk (IRR(medium vs. low) 1.5, 95%CI 0.92-2.4; IRR(high vs. low) 3.0, 95%CI 2.0-4.6). Among the 161 observed seroconversions, 28% reported no symptoms of COVID-like illness (i.e., were asymptomatic), and 27% reported a positive SARS-CoV-2 diagnostic test. Ultimately, only 29% reported isolating and 19% were asked about contacts.
INTERPRETATION: Modifiable epidemiologic risk factors and poor reach of public health strategies drove SARS-CoV-2 transmission across the U.S during May 2020-January 2021.


Reference Type

Journal Article

Year Published


Journal Title



Nash, Denis
Rane, Madhura
Chang, Mindy
Kulkarni, Sarah Gorrell
Zimba, Rebecca
You, William
Berry, Amanda
Mirzayi, Chloe
Kochhar, Shivani
Maroko, Andrew
Robertson, McKaylee
Westmoreland, Drew
Parcesepe, Angela M.
Waldron, Levi
Grov, Christian

Article Type




Data Set/Study

Communities, Households and SARS/CoV-2 Epidemiology (CHASING) COVID Cohort Study


United States of America




Parcesepe - 0000-0002-4321-125x