Estimating the cumulative incidence of SARS-CoV-2 infection and the infection fatality ratio in light of waning antibodies.

• Type of Material: Article
• Authors: Kayoko Shioda, Gangarosa Department of Environmental Health, Rollins School of Public Health, Emory University; Siu Lau, Emory University; Alicia NM. Kraay, Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, USA.; Kristin Nelson, Emory University; Aaron Siegler, Emory University; Patrick Sullivan, Emory University; Matthew Collins, Emory University; Joshua S. Weitz, School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA; School of Physics, Georgia Institute of Technology; Benjamin Lopman, Emory University
• Language: English
• Date: 2020-11-16
• Publisher: NIH
• Publication Version: Preprint (Prior to Peer Review)
• Copyright Statement: 2020
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1101/2020.11.13.20231266
• Title of Journal or Parent Work: medRxiv
• Grant/Funding Information: This study was supported by the US National Science Foundation [grant 2032082 to JSW and grant 2032084 to BAL] and the US National Institute of Allergy and Infectious Diseases [3R01AI143875-02S1 to PSS and AJS].
• Research Categories: Health Sciences, Immunology; Health Sciences, Public Health

Abstract

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.