Six-month antibody response to SARS-CoV-2 in healthcare workers assessed by virus neutralisation and commercial assays

We conducted a prospective study in healthcare workers (n=296) of the University Hospital of Lyon, France. Serum samples (n=296) collected six months after disease onset were tested using three commercial assays: the Wantai Ab assay detecting total antibodies against the receptor binding domain (RBD) of the S protein, the bioMerieux Vidas assay detecting IgG to the RBD and the Abbott Architect assay detecting IgG to the N protein. The neutralising antibody (NAb) titre was also determined for all samples with a virus neutralisation assay (VNA) using live virus. The positivity rate was 100% with the Wantai assay, 84.8% with the bioMerieux assay and 55.4% with the Abbott assay. Only 51% of HCWs were positive for the presence of NAb. Less than 10 % of HCWs had a NAb titre greater than 80. At a neutralising titre of 80, the area under the curves [IC 95%] was 0.71 [0.62-0.81], 0.75 [0.65-0.85] and 0.95 [0.92-0.97] for Wantai, Abbott and Vidas respectively. The data presented herein suggest that commercial assays detecting antibodies against the N protein must not be used in long-term seroprevalence surveys while the Wantai assay could be useful for this purpose. VNA should remain the gold standard to assess the protective antibody response, but some commercial assays could be used as first-line screening of long-term presence of NAb. ### Competing Interest Statement Antonin Bal has received grant from bioMerieux and has served as consultant for bioMerieux for work and research not related to this manuscript. Sophie Trouillet-Assant has received research grant from bioMerieux concerning previous works not related to this manuscript. The other authors have no relevant affiliations or financial involvement with any organisation or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. ### Clinical Trial NCT04341142 ### Funding Statement This research is being supported by Hospices Civils de Lyon and by Fondation des Hospices Civils de Lyon.  ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Written informed consent was obtained from all participants; ethics approval was obtained from the national review board for biomedical research in April 2020 (Comite de Protection des Personnes Sud Mediterranee I, Marseille, France; ID RCB 2020-A00932-37), and the study was registered on ClinicalTrials.gov ([NCT04341142][1]). All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data are available in the manuscript. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT04341142&atom=%2Fmedrxiv%2Fearly%2F2020%2F12%2F09%2F2020.12.08.20245811.1.atom