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PubMed; 2020.
Preprint in English | PubMed | ID: ppcovidwho-333609


BACKGROUND: Serology tests can identify previous infections and facilitate estimation of the number of total infections. However, immunoglobulins targeting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been reported to wane below the detectable level of serological assays. We estimate the cumulative incidence of SARS-CoV-2 infection from serology studies, accounting for expected levels of antibody acquisition (seroconversion) and waning (seroreversion), and apply this framework using data from New York City (NYC) and Connecticut. METHODS: We estimated time from seroconversion to seroreversion and infection fatality ratio (IFR) using mortality data from March-October 2020 and population-level cross-sectional seroprevalence data from April-August 2020 in NYC and Connecticut. We then estimated the daily seroprevalence and cumulative incidence of SARS-CoV-2 infection. FINDINGS: The estimated average time from seroconversion to seroreversion was 3-4 months. The estimated IFR was 1.1% (95% credible interval: 1.0-1.2%) in NYC and 1.4% (1.1-1.7%) in Connecticut. The estimated daily seroprevalence declined after a peak in the spring. The estimated cumulative incidence reached 26.8% (24.2-29.7%) and 8.8% (7.1-11.3%) at the end of September in NYC and Connecticut, higher than maximum seroprevalence measures (22.1% and 6.1%), respectively. INTERPRETATION: The cumulative incidence of SARS-CoV-2 infection is underestimated using cross-sectional serology data without adjustment for waning antibodies. Our approach can help quantify the magnitude of underestimation and adjust estimates for waning antibodies. FUNDING: This study was supported by the US National Science Foundation and the National Institute of Allergy and Infectious Diseases.

PubMed; 2022.
Preprint in English | PubMed | ID: ppcovidwho-332469


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.

Preprint in English | MEDLINE | ID: ppcovidwho-326567


Since its emergence and detection in Wuhan, China in late 2019, the novel coronavirus SARS-CoV-2 has spread to nearly every country around the world, resulting in hundreds of thousands of infections to date. The virus was first detected in the Pacific Northwest region of the United States in January, 2020, with subsequent COVID-19 outbreaks detected in all 50 states by early March. To uncover the sources of SARS-CoV-2 introductions and patterns of spread within the U.S., we sequenced nine viral genomes from early reported COVID-19 patients in Connecticut. Our phylogenetic analysis places the majority of these genomes with viruses sequenced from Washington state. By coupling our genomic data with domestic and international travel patterns, we show that early SARS-CoV-2 transmission in Connecticut was likely driven by domestic introductions. Moreover, the risk of domestic importation to Connecticut exceeded that of international importation by mid-March regardless of our estimated impacts of federal travel restrictions. This study provides evidence for widespread, sustained transmission of SARS-CoV-2 within the U.S. and highlights the critical need for local surveillance.

Topics in Antiviral Medicine ; 29(1):246, 2021.
Article in English | EMBASE | ID: covidwho-1250755


Background: Understanding the cumulative incidence of SARS-CoV-2 infections in the United States has been limited by asymptomatic infections, waning antibodies after natural infection, incomplete case ascertainment and reporting, and limited representative samples. We conducted a probability survey of US households to measure SARS-CoV-2 infection and immune response and to estimate the cumulative incidence of SARS-CoV-2 infection. Methods: A multistage random sample of US postal addresses were mailed a kit to self-collect an anterior nares swab and a dried blood spot (DBS) sample from August to December 2020. Specimens were tested by EUA-approved PCR and serology tests. Weighted estimates of antibody prevalence, together with historical patterns of antibody waning, were used to estimate the cumulative incidence of SARS-CoV-2 infections, the diagnosed fraction, and infection fatality ratio (IFR). Weighted estimates were used to calculate prevalence ratios comparing demographic, geographic, and clinical subgroups. Results: 37,056 kits were mailed to sampled US households. Overall, 5,666 surveys were completed by December 8, 2020;of these, 4,654 also returned a DBS specimen with a valid antibody result. Overall participation rate was 11.8%. We estimated 39,421,841 (95% credible interval (CrI): 33,759,801-43,958,068) total infections by October 30, 2020, an estimated diagnosed fraction of 17% (95% Crl: 15-21%) and an estimated IFR of 0.64% (95% CrI: 0.58-0.75%). Daily seroprevalence peaked by Sept 2020 and remained stable through November 2020 due to a balance of waning antibodies and new infections (Figure). Non- Hispanic Black (PR: 2.2;95% confidence interval (CI): 1.2-4.0) and Hispanic (PR: 3.1, CI: 1.8-5.3) respondents were more likely than White non-Hispanic to have laboratory evidence of prior SARS-CoV-2 infection. Prevalence was also higher among those living in metropolitan areas (PR vs non-metropolitan areas: 2.5, CI: 1.3-5.0) and among those reporting cold or flu symptoms (PR: 2.6, CI: 1.6-4.1) or loss of taste or smell (PR: 12.8, CI: 8.5-19.4) since January 1, 2020. Conclusion: We report the results of the first national probability sample of US households to assess the prevalence of antibodies to SARS-CoV-2 and cumulative incidence. As of October 30, 2020, about 1 in 8 US residents aged ≥18 years had been infected with SARS-CoV-2, and about 1 in 6 of those had been diagnosed. Household-based probability surveys provide a minimally biased benchmark to characterize epidemic dynamics.

Topics in Antiviral Medicine ; 29(1):247, 2021.
Article in English | EMBASE | ID: covidwho-1250708


Background: Developing representative estimates of COVID-19 vaccine acceptance will be essential to public health planning as the vaccine supply moves towards sufficiency in meeting initial levels of demand. We conducted a national probability household survey to assess vaccine willingness and history of SARS-CoV-2 infection based on antibody response. Methods: Study materials were sent to an address-based sample frame that includes nearly all residential addresses in the US. Participants completed a behavioral survey and dried blood spot (DBS) specimen collection for SARS-CoV-2 antibody testing during the study period, August 9 - December 8, 2020. Vaccine willingness was measured with a 5-point Likert scale item with responses ranging from “Very unlikely” to “Very likely.” Sample weights were calculated and applied to descriptive statistics and prevalence ratios (PR). We categorized persons as either Ig negative, Ig positive and aware of prior COVID-19 infection, or Ig positive and unaware of prior COVID-19 infection. Results: A total of 4,654 respondents completed the survey and had a valid antibody test result, representing 242,875,582 US adults. Overall, a substantial proportion, 32% (76,967,749 adults), were unsure or unwilling to receive a COVID-19 vaccine. Many groups at increased risk for SARS-CoV-2 had higher proportions unsure or unwilling, including Black (46%) relative to White (30%, p<.001) race, persons working outside home (38%) relative to at home (21%, p<.001), and smokers (44%) relative to nonsmokers (29%, p<.001) (Table 1). Dissonance between transmission risk and vaccine willingness was also observed in biologic data. Persons Ig positive (previously infected) and unaware of their status had a higher point estimate of unwillingness to be vaccinated (39%) than persons Ig negative with no history of infection (31%, p=.28). Overall, we estimate 12% (29,241,030 adults) were very unlikely to be vaccinated, 7% (15,729,748) were somewhat unlikely, 13% (31,996,971) were unsure, 19% (44,958,518) were likely, and 50% (119,820,865) were very likely. Conclusion: In the first national probability survey with biomarker data, we demonstrated that many groups with higher risk for COVID-19 infection had lower willingness to take a COVID-19 vaccine. This finding is in accordance with pre-existing fault-lines of inequity in our society. Substantial vaccine uptake promotion is needed, and should be targeted to address inequities correlated with vaccine willingness.