and L.G., with input from all co-authors. Funding LG was supported by the Wellcome Trust (201470/Z/16/Z), the National Institute of Allergy and Infectious Diseases of the National Institutes of Health under award number 1R01AI146338, the GOSH Charity (VC0921) and the GOSH/ICH Biomedical Research Centre (www.nihr.ac.uk). Spike (Roche-S) assays and the Abbott Nucleoprotein assay (Abbott-N) on serial positive monthly samples collected as part of the Co-STARs study (www.clinicaltrials.gov, NCT04380896) up to 200?days following infection. Our findings demonstrate the considerable effect of time since symptom onset on the diagnostic sensitivity of different assays. Using a time-to-event analysis, we demonstrated that 50% of the Abbott nucleoprotein assays will give a negative result after 175?days (median survival time 95% CI 168C185?days), compared to the better performance over time of the Roche Elecsys nucleoprotein assay (93% survival probability at 200?days, 95% CI 88C97%). Assays targeting the spike protein showed a lower decline over the follow-up period, both for the MSD spike assay (97% survival probability at 200?days, 95% CI 95C99%) and the Roche Elecsys spike assay (95% survival probability at 200?days, 95% CI 93C97%). The best performing quantitative Roche Elecsys Spike assay showed no evidence of waning Spike antibody titers over the 200-day time course of the study. We have shown that compared to other assays evaluated, the Abbott-N assay fails to detect SARS-CoV-2 antibodies as time passes since infection. In contrast the Roche Elecsys Spike Assay and the MSD assay maintained a high sensitivity for the 200-day duration of the study. These limitations of the Abbott assay should be considered when quantifying the immune correlates of protection or the need for SARS-CoV-2 antibody therapy. The high levels of maintained detectable neutralizing spike antibody titers identified by the quantitative Roche Elecsys assay is encouraging and provides further evidence in support of long-lasting SARS-CoV-2 protection following natural infection. Subject terms: Infectious diseases, Viral infection Introduction Following natural infection or vaccination, sensitive measurement of SARS-CoV-2 serological status is important to identify immune correlates of protection from future waves of the pandemic, evaluate those in need of booster vaccination and identify candidates for SARS-CoV-2 antibody therapy. The rapid response to the COVID-19 pandemic has led to the development of a wide range of serological tests suitable for evaluating SARS-CoV-2 exposure, infection or vaccination status1C3. Typically, these tests are approved for use by the regulatory authorities based on their performance against a panel of reference sera including positive and negative controls at either 14- or 21-days post infection4. Public Health England reported a 93.9% sensitivity for the Abbott SARS-CoV-2 IgG Nucleoprotein assay5 and 100% for the Roche Elecsys Nucleoprotein assay at??14?days post infection6. This led to widespread adoption of these tests across NHS laboratories for testing at population level. Other studies have confirmed this test performance at 14C21?days post infection7,8. Population level serological studies have also based their conclusionsvital to guide national policyon the basis of these tests9 Zofenopril without considering how time since infection influences the performance of the test. The problem with this approach is definitely that it does not take into account SARS-CoV-2 humoral dynamics and changes in avidity over time10,11. Although serological checks with limited diagnostic range may demonstrate superb level of sensitivity shortly after illness, it is unclear Zofenopril how Zofenopril they will perform with time following illness or vaccination. In order to address this query, we applied 4 widely used serological assays in parallel to serial samples from your Co-STARs study12 in which staff screening seropositive to SARS-CoV-2 were followed for up to 200?days following illness. We compared the proportion of samples that remained seropositive over time using a survival analysis and identified the decay rate of the nucleoprotein (N) antibody and the spike (S) antibody for each test using a previously published mathematical model fitted to the data. Materials and methods Study setting and design Serological screening was performed on stored serum samples collected as part of the Co-STARs study (www.clinicaltrials.gov, NCT04380896), Zofenopril approved by the UK National Health Service Health Study Authority and run at Great Ormond Street Hospital between April 29th and November 2020 in accordance with the relevant recommendations10. Briefly, Co-STARs was a 1-12 months single-centre prospective cohort study of antibody reactions to COVID-19 illness in healthcare workers. Serum samples were taken from the 3657 participants at baseline and underwent a screening ELISA using the EDI assay. Repeated regular LILRA1 antibody monthly serum samples were then taken from.