Nationally Representative Social Contact Patterns among U.S. adults, August 2020-April 2021 (preprint)

The response to the COVID-19 pandemic in the U.S prompted abrupt and dramatic changes to social contact patterns. Monitoring changing social behavior is essential to provide reliable input data for mechanistic models of infectious disease, which have been increasingly used to support public health policy to mitigate the impacts of the pandemic. While some studies have reported on changing contact patterns throughout the pandemic., few have reported on differences in contact patterns among key demographic groups and none have reported nationally representative estimates. We conducted a national probability survey of US households and collected information on social contact patterns during two time periods: August-December 2020 (before widespread vaccine availability) and March-April 2021 (during national vaccine rollout). Overall, contact rates in Spring 2021 were similar to those in Fall 2020, with most contacts reported at work. Persons identifying as non-White, non-Black, non-Asian, and non-Hispanic reported high numbers of contacts relative to other racial and ethnic groups. Contact rates were highest in those reporting occupations in retail, hospitality and food service, and transportation. Those testing positive for SARS-CoV-2 antibodies reported a higher number of daily contacts than those who were seronegative. Our findings provide evidence for differences in social behavior among demographic groups, highlighting the profound disparities that have become the hallmark of the COVID-19 pandemic.

Cumulative incidence of SARS-CoV-2 infections among adults in Georgia, USA, August-December 2020 (preprint)

Background: Reported COVID-19 cases underestimate the true number of SARS-CoV-2 infections. Data on all infections, including asymptomatic infection, are needed to guide state testing and prevention programs. To minimize biases in estimates from seroprevalence surveys and reported cases, we conducted a state-wide probability survey of Georgia households and estimated cumulative incidence of SARS-CoV-2 infections adjusted for antibody waning. Methods: From August to December 2020, we mailed kits to self-collect specimens (nasal swabs and blood spots) to a random sample of Georgia addresses. One randomly-selected adult household member completed a survey and returned specimens for virus and antibody testing. We estimated cumulative incidence of SARS-CoV-2 infections adjusted for waning antibodies, reported fraction, and infection fatality ratio (IFR). Differences in seropositivity among demographic, geographic and clinical subgroups were explored with weighted prevalence ratios (PR). Results: Among 1,370 Georgia adult participants, adjusted cumulative incidence of SARS-CoV-2 was 16.1% (95% credible interval (CrI): 13.5-19.2%) as of November 16, 2020. The reported fraction was 26.6% and IFR was 0.78%. Non-Hispanic Black (PR: 2.03, CI 1.0, 4.1) and Hispanic adults (PR: 1.98, CI 0.74, 5.31) were more likely than non-Hispanic White adults to be seropositive. Seropositivity in metropolitan Atlanta's Fulton and DeKalb counties was similar to seropositivity elsewhere in Georgia (7.8% vs. 8.8%). Conclusions: As of mid-November 2020, one in 6 adults in Georgia had been infected with SARS-CoV-2. The scope of the COVID-19 epidemic in Georgia is likely substantially underestimated by reported cases.

SARS-CoV-2 Cumulative Incidence, United States, August-December 2020 (preprint)

Background: Reported COVID-19 cases underestimate SARS-CoV-2 infections. We conducted a national probability survey of US households to estimate the cumulative incidence of infection adjusted for antibody waning.Methods: From August to December 2020, a multistage random sample of US addresses were mailed a survey and materials to self-collect nasal swabs and dried blood spots. One adult household member was randomly selected to complete the survey and mail specimens for virus and antibody testing. We estimated cumulative incidence of SARS-CoV-2 infections adjusted for waning antibodies and calculated reported fraction and infection fatality ratio (IFR). Differences in seropositivity among demographic, geographic and clinical subgroups were explored with weighted prevalence ratios (PR).Results: Among 39,500 sampled households, 4,654 respondents provided surveys and valid specimens. Cumulative incidence adjusted for waning was 11.9% (95% credible interval (CrI): 10.5-13.5%) as of October 30, 2020. We estimated 30,332,842 (95% CrI: 26,703,753-34,335,338) total infections in the U.S. adult population by October 30, 2020.The reported fraction was 17% and the IFR was 0.85% among adults. Non-Hispanic Black (PR: 2.2) and Hispanic (PR: 3.1) persons were significantly more likely than White non-Hispanic to be seropositive, as were those living in metropolitan areas (PR: 2.5).Conclusions: One in 8 US adults had been infected with SARS-CoV-2, but few had been accounted for in public health reporting. Our data document that the scope of the COVID-19 pandemic is likely substantially underestimated by reported cases. Disparities in COVID-19 by race observed among reported cases cannot be attributed to differential diagnosis or reporting of infections in some population subgroups.Funding Statement: This project was funded by the National Institute of Allergy andInfectious Diseases, grant number 3R01AI143875-02S1, This project was partially funded by The Epidemiology and Laboratory Capacity for Infectious Diseases, Grant Number 6 NU50CK000539. This project was partially funded by the Woodruff Foundation.Declaration of Interests: The authors declare no conflict of interest.Ethics Approval Statement: The COVIDVu study was approved by the Emory University Institutional Review Board (STUDY00000695).

Willingness to seek laboratory testing for SARS-CoV-2 with home, drive-through, and clinic-based specimen collection locations (preprint)

BackgroundSARS-CoV-2 virus testing for persons with COVID-19 symptoms, and contact tracing for those testing positive, will be critical to successful epidemic control. Willingness of persons experiencing symptoms to seek testing may determine the success of this strategy. MethodsA cross-sectional, online survey in the United States measured willingness to seek testing if feeling ill under different specimen collection scenarios: home-based saliva, home-based swab, drive-through facility swab, and clinic-based swab. Instructions clarified that home-collected specimens would be mailed to a laboratory for testing. We presented similar willingness questions regarding testing during follow-up care. ResultsOf 1435 participants, comprising a broad range of sociodemographic groups, 92% were willing to test with a home saliva specimen, 88% with home swab, 71% with drive-through swab, and 60% with clinic collected swab. Moreover, 68% indicated they would be more likely to get tested if there was a home testing option. There were no significant differences in willingness items across sociodemographic variables or for those currently experiencing COVID-19 symptoms. Results were nearly identical for willingness to receive testing for follow-up COVID-19 care. ConclusionsWe observed a hierarchy of willingness to test for SARS-CoV-2, ordered by the degree of contact required. Home specimen collection options could result in up to one-third more symptomatic persons seeking testing, facilitating contact tracing and optimal clinical care. Remote specimen collection options may ease supply chain challenges and decrease the likelihood of nosocomial transmission. As home specimen collection options receive regulatory approval, they should be scaled rapidly by health systems.