Decline in SARS-CoV-2 Antibodies After Mild Infection Among Frontline Health Care Personnel in a Multistate Hospital Network — 12 States, April–August 2020
Authors: Wesley H. Self, Mark W. Tenforde, William B. Stubblefield, Leora R. Feldstein, Jay S. Steingrub, Nathan I. Shapiro, Adit A. Ginde, Matthew E. Prekker, Samuel M. Brown, Ithan D. Peltan, Michelle N. Gong, Michael S. Aboodi, Akram Khan, Matthew C. Exline, D. Clark Files, Kevin W. Gibbs, Christopher J. Lindsell, Todd W. Rice, Ian D. Jones, Natasha Halasa, H. Keipp Talbot, Carlos G. Grijalva, Jonathan D. Casey, David N. Hager, Nida Qadir, Daniel J. Henning, Melissa M. Coughlin, Jarad Schiffer, Vera Semenova, Han Li, Natalie J. Thornburg, Manish M. Patel, Mohammed Ata Ur Rasheed, Lisa Mills, Sandra N. Lester, Brandi Freeman, Bailey Alston, Muyiwa Ategbole, Peter Browning, Shanna Bolcen, Darbi Boulay, Li Cronin, Ebenezer David, Rita Desai, Monica Epperson, Yamini Gorantla, Tao Jia, Pete Maniatis, Kristina Ortiz, So Hee Park, Palak Patel, Yunlong Qin, Heather Tatum, Briana Zellner, Adrienne Baughman, Kimberly W. Hart, Robert McClellan, Rendie McHenry, Jakea Johnson, Andrea Fletcher, Kemberlyne Cordero, Lori Kozikowski, Lesley De Souza, Sarah Romain, Scott Ouellette, Andres Santana, Sherell Thornton-Thompson, Michelle Howell, Jennifer Peers, Shelby Shelton, Lani Finck, Kirsten Soules, Michael Klausner, Ximena Calderon-Morales, Heidi L. Erickson, Audrey Hendrickson, Jamie Stang, Ellen Maruggi, Alex Dunn, Eddie Stenehjem, Valerie Aston, Mikaele Bown, Michelle Matheu, Rilee Smith, Olivia Krol, Andrew Salar, Makrina Kamel, Kelly Nguyen, Peter Huynh, Sarah Karow, Michelle Bright, Holly Bookless, Sandy Mullins, Kelly Neidert, Dina McGowan, Elizabeth Cassandra, Emily Brown, Claire Carlin, Trina Wemlinger, Breona Edwards, Lori Flores, Mary LaRose, Kathie J. Ferbas, Rachel Martin-Blais, Grace M. Aldrovandi, Olivia Thompson, Sakshi Sehgal
Journal: MMWR Morbidity and Mortality Weekly Report (2020)

Most persons infected with SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), develop virus-specific antibodies within several weeks, but antibody titers might decline over time. Understanding the timeline of antibody decline is important for interpreting SARS-CoV-2 serology results. Serum specimens were collected from a convenience sample of frontline health care personnel at 13 hospitals and tested for antibodies to SARS-CoV-2 during April 3-June 19, 2020, and again approximately 60 days later to assess this timeline. The percentage of participants who experienced seroreversion, defined as an antibody signal-to-threshold ratio >1.0 at baseline and <1.0 at the follow-up visit, was assessed. Overall, 194 (6.0%) of 3,248 participants had detectable antibodies to SARS-CoV-2 at baseline (1). Upon repeat testing approximately 60 days later (range = 50-91 days), 146 (93.6%) of 156 participants experienced a decline in antibody response indicated by a lower signal-to-threshold ratio at the follow-up visit, compared with the baseline visit, and 44 (28.2%) experienced seroreversion. Participants with higher initial antibody responses were more likely to have antibodies detected at the follow-up test than were those who had a lower initial antibody response. Whether decay in these antibodies increases risk for reinfection and disease remains unanswered. However, these results suggest that serology testing at a single time point is likely to underestimate the number of persons with previous SARS-CoV-2 infection, and a negative serologic test result might not reliably exclude prior infection.