Résumé
ABSTRACT Importance Understanding how SARS-CoV-2 seroprevalence varies regionally across California is critical to the public health response to the pandemic. Objective To estimate how many Californians have antibodies against SARS-CoV-2 from prior infection or vaccination. Design Wave 1 of CalScope: a repeated cross-sectional serosurvey of adults and children enrolled between April 20, 2021 and June 16, 2021. Setting A population-based random sample of households in seven counties in California (Alameda, El Dorado, Kern, Los Angeles, Monterey, San Diego, and Shasta) were invited to complete an at-home SARS-CoV-2 antibody test and survey instrument. Participants Invitations were sent to 200,000 randomly selected households in the seven counties. From each household, 1 adult (18 years and older) and 1 child (aged 6 months to 17 years) could enroll in the study. There were no exclusion criteria. Main Outcome(s) and Measures All specimens were tested for antibodies against the nucleocapsid and spike proteins of SARS-CoV-2. The primary outcome was serostatus category, which was determined based on antibody test results and self-reported vaccination status: seronegative, antibodies from infection only, antibodies from infection and vaccination, and antibodies from vaccination alone. We used inverse probability of selection weights and iterative proportional fitting to account for non-response. Results 11,161 households enrolled in wave 1 of CalScope, with 7,483 adults and 1,375 children completing antibody testing. As of June 2021, 27% (95%CI [23%, 31%]) of adults and 30% (95%CI [24%, 36%]) of children had evidence of prior SARS-CoV-2 infection; 33% (95%CI [28%, 37%]) of adults and 57% (95%CI [48%, 66%]) of children were seronegative. Serostatus varied regionally. Californians 65 years or older were most likely to have antibodies from vaccine alone (59%; 95%CI [48%, 69%]) and children between 5-11 years old were most likely to have antibodies from prior infection alone (36%; 95%CI [21%, 52%]). Conclusions and Relevance As of June 2021, a third of adults in California and most children under 18 remained seronegative. Seroprevalence varied regionally and by demographic group, suggesting that some regions or populations might remain more vulnerable to subsequent surges than others. Key Points Question What is the prevalence of vaccine and infection derived antibodies against SARS-CoV-2 in adults and children in California? Findings In this population-based serosurvey that included 11,161 households, as of June 2021, 33% of adults and 57% of children were seronegative; 18% of adults and 26% of children had antibodies from infection alone; 9% of adults and 5% of children had antibodies from both infection and vaccination; and 41% of adults and 13% of children had antibodies from vaccination alone. Meaning Serostatus varied considerably across geographic regions, suggesting that certain areas might be at increased risk for future COVID-19 surges.
Sujets)
COVID-19Résumé
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).