Decline in SARS-CoV-2 Antibodies After Mild Infection Among Frontline Health Care Personnel in a Multistate Hospital Network — 12 States, April–August 2020

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

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.