• Sheila F Lumley, Jia Wei, Denise O'Donnell, Nicole E Stoesser, Philippa C Matthews, Alison Howarth, Stephanie B Hatch, Brian D Marsden, Stuart Cox, Tim James, Liam J Peck, Thomas G Ritter, Zoe de Toledo, Richard J Cornall, E Yvonne Jones, David I Stuart, Gavin Screaton, Daniel Ebner, Sarah Hoosdally, Derrick W Crook, Christopher P Conlon, Koen B Pouwels, A Sarah Walker, PetoTim E ATEANuffield Department of Medicine, University of Oxford, Oxford, United Kingdom.National Institute for Health Research (NIHR) Oxford Biomedical Research Centre, University of Oxford, Oxford, United Kingdom.NIHR Health Protection Research Unit , Timothy M Walker, Katie Jeffery, David W Eyre, and Oxford University Hospitals Staff Testing Group.
• Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom.
• Clin. Infect. Dis. 2021 Aug 2; 73 (3): e699-e709.

BackgroundSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunoglobulin G (IgG) antibody measurements can be used to estimate the proportion of a population exposed or infected and may be informative about the risk of future infection. Previous estimates of the duration of antibody responses vary.MethodsWe present 6 months of data from a longitudinal seroprevalence study of 3276 UK healthcare workers (HCWs). Serial measurements of SARS-CoV-2 anti-nucleocapsid and anti-spike IgG were obtained. Interval censored survival analysis was used to investigate the duration of detectable responses. Additionally, Bayesian mixed linear models were used to investigate anti-nucleocapsid waning.ResultsAnti-spike IgG levels remained stably detected after a positive result, for example, in 94% (95% credibility interval [CrI] 91-96%) of HCWs at 180 days. Anti-nucleocapsid IgG levels rose to a peak at 24 (95% CrI 19-31) days post first polymerase chain reaction (PCR)-positive test, before beginning to fall. Considering 452 anti-nucleocapsid seropositive HCWs over a median of 121 days from their maximum positive IgG titer, the mean estimated antibody half-life was 85 (95% CrI 81-90) days. Higher maximum observed anti-nucleocapsid titers were associated with longer estimated antibody half-lives. Increasing age, Asian ethnicity, and prior self-reported symptoms were independently associated with higher maximum anti-nucleocapsid levels and increasing age and a positive PCR test undertaken for symptoms with longer anti-nucleocapsid half-lives.ConclusionsSARS-CoV-2 anti-nucleocapsid antibodies wane within months and fall faster in younger adults and those without symptoms. However, anti-spike IgG remains stably detected. Ongoing longitudinal studies are required to track the long-term duration of antibody levels and their association with immunity to SARS-CoV-2 reinfection.© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.

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