TY - JOUR
T1 - Specific thresholds of circulating antibody titers predict against infection and reduced disease severity in SARS-CoV-2 close contacts
AU - Byrne, Joanne
AU - Gaillard, Colette Marie
AU - Gu, Lili
AU - Garcia-Leon, Alejandro
AU - Casey, Orlaith
AU - Kenny, Grace
AU - Saini, Gurvin
AU - Alalwan, Dana
AU - O'Gorman, Tessa
AU - O'Regan, Siobhan
AU - Doran, Peter
AU - Feeney, Eoin R.
AU - O'Halloran, Jane A.
AU - Horgan, Mary
AU - Cotter, Aoife G.
AU - de Barra, Eoghan
AU - Sadlier, Corinna
AU - Landay, Alan
AU - Gautier, Virginie
AU - Mallon, Patrick W.G.
N1 - Publisher Copyright:
© The Author(s) 2025. Published by Oxford University Press on behalf of The American Association of Immunologists.
PY - 2025/9/1
Y1 - 2025/9/1
N2 - Higher circulating SARS-CoV-2 IgG titers correlate with SARS-CoV-2 ex vivo viral neutralization, but how well this translates to clinical protection in the real-world setting is unclear. In a prospective cohort study, we enrolled 44 SARS-CoV-2 negative, confirmed SARS-CoV-2 close contacts. Receptor-binding domain (RBD) and full-spike IgG and SARS-CoV-2 memory B-cell frequencies were measured at exposure, and participants were serially tested for incident infection over 14 days. Those who developed SARS-CoV-2 infection had significantly lower RBD titers, but not memory B-cell frequencies. An RBD IgG titer >6321 BAU/ml was associated with a reduced SARS-CoV-2 acquisition risk (HR 0.32, 95% CI 0.13-0.81), while an RBD IgG titer >456 BAU/ml was associated with a reduced moderate or severe COVID-19 risk (HR 0.15, 95% CI 0.03-0.81), identifying this threshold as a correlate of protection.
AB - Higher circulating SARS-CoV-2 IgG titers correlate with SARS-CoV-2 ex vivo viral neutralization, but how well this translates to clinical protection in the real-world setting is unclear. In a prospective cohort study, we enrolled 44 SARS-CoV-2 negative, confirmed SARS-CoV-2 close contacts. Receptor-binding domain (RBD) and full-spike IgG and SARS-CoV-2 memory B-cell frequencies were measured at exposure, and participants were serially tested for incident infection over 14 days. Those who developed SARS-CoV-2 infection had significantly lower RBD titers, but not memory B-cell frequencies. An RBD IgG titer >6321 BAU/ml was associated with a reduced SARS-CoV-2 acquisition risk (HR 0.32, 95% CI 0.13-0.81), while an RBD IgG titer >456 BAU/ml was associated with a reduced moderate or severe COVID-19 risk (HR 0.15, 95% CI 0.03-0.81), identifying this threshold as a correlate of protection.
KW - antibodies
KW - B cells
KW - COVID-19
KW - SARS-CoV-2
UR - https://www.scopus.com/pages/publications/105017704355
UR - https://www.scopus.com/pages/publications/105017704355#tab=citedBy
U2 - 10.1093/jimmun/vkaf101
DO - 10.1093/jimmun/vkaf101
M3 - Article
C2 - 40405410
AN - SCOPUS:105017704355
SN - 0022-1767
VL - 214
SP - 2238
EP - 2243
JO - Journal of immunology (Baltimore, Md. : 1950)
JF - Journal of immunology (Baltimore, Md. : 1950)
IS - 9
ER -