Antibody Persistence in the Six Months Following SARS-CoV-2 Infection among Hospital Workers

Background: Little is known about the duration and breadth of humoral immunity against SARS-CoV-2 to better inform appropriate pandemic control measures.Methods: We measured anti-RBD, -N and neutralizing antibodies at one, three and six months after mostly mild COVID-19 in 200 hospital workers using commercial ELISAs and a surrogate virus neutralization assay.Findings: Anti-RBD antibodies were detected in all participants at each timepoint. Geometric mean concentrations (GMCs) progressively increased between month one (74 . 2 U/ml [95%CI 62 . 7-87 . 8), three (103 . 2 U/ml [95%CI 87 . 9-121 . 2]; p<0 . 001), and six (123 . 3 U/ml [95%CI 103 . 4-147 . 0]; p<0 . 001) in the whole cohort. Anti-N antibodies were detectable in >97% at all times. Neutralizing antibodies were detectable in 92 . 5% (184/199), 94 . 4% (185/196) and 76 . 5% (150/196) participants at one, three and six months, respectively. Their GMC progressively decreased between months one (20 . 1 AU/ml [95%CI 16 . 9-24 . 0]), three (15 . 2 AU/ml [95%CI 13 . 2-17 . 6]; p<0 . 001) and six (9 . 4 AU/ml [95%CI 7 . 7-11 . 4]; p<0 . 001). Neutralizing antibody and anti-RBD concentrations strongly correlated at each timepoint (all r>0 . 86, p<0 . 001). Disease severity was associated with higher initial anti-RBD and neutralizing concentrations, but not with their kinetics.Interpretation: Neutralizing antibodies persisted at six months in most participants, indicating more durability than initially feared. Anti-RBD antibodies persisted better and even increased over time, possibly related to the preferential detection of progressively higher-affinity antibodies. Trial Registration: registered (NCT04329546)Funding: Pictet, Ancrage and Schmidheiny Foundations, Geneva University Hospitals' Private Foundation, PRD, Center for Vaccinology and Centre for Emerging Viral Diseases.Declaration of Interests: The authors have no conflict of interest.Ethics Approval Statement: The study was approved by the local ethics committee (CCER 2020-00516) and registered (NCT04329546) prior to initiation. All hospital workers provided written informed consent before enrolment.