The duration, dynamics and determinants of SARS-CoV-2 antibody responses in individual healthcare workers
Lumley SF., Wei J., O’Donnell D., Stoesser NE., Matthews PC., Howarth A., Hatch SB., Marsden BD., Cox S., James T., Peck LJ., Ritter TG., de Toledo Z., Cornall RJ., Jones EY., Stuart DI., Screaton G., Ebner D., Hoosdally S., Crook DW., Conlon CP., Pouwels KB., Walker AS., Peto TEA., Walker TM., Jeffery K., Eyre DW.
<jats:title>Abstract</jats:title> <jats:sec> <jats:title>Background</jats:title> <jats:p>SARS-CoV-2 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.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>We 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.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Anti-spike IgG levels remained stably detected after a positive result, e.g., in 94% (95% credibility interval, CrI, 91-96%) of HCWs at 180 days. Anti-nucleocapsid IgG levels rose to a peak at 24 (95% credibility interval, CrI 19-31) days post first PCR-positive test, before beginning to fall. Considering 452 anti-nucleocapsid seropositive HCWs over a median of 121 days from their maximum positive IgG titre, the mean estimated antibody half-life was 85 (95%CrI, 81-90) days. Higher maximum observed anti-nucleocapsid titres 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.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusion</jats:title> <jats:p>SARS-CoV-2 anti-nucleocapsid antibodies wane within months, and 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.</jats:p> </jats:sec>