3 sars-cov-2 igg detection in human oral fluids . 51

57 Seroepidemiological studies to monitor antibody kinetics are important for assessing the extent and 58 spread of SARS-CoV-2 in a population. Non-invasive sampling methods are advantageous to reduce 59 the need for venepuncture, which may be a barrier to investigations particularly in paediatric 60 populations. Oral Fluids are obtained by gingiva-crevicular sampling from children and adults and are 61 very well accepted. ELISA based on these samples have acceptable sensitivity and specificity 62 compared to conventional serum-based antibody ELISAs and are suitable for population-based 63 surveillance. 64 We describe the development and evaluation of SARS-COV-2 IgG ELISAs using SARS-CoV-2 viral 65 nucleoprotein (NP) and spike (S) proteins in IgG isotype capture format and an indirect receptor66 binding-domain (RBD) IgG ELISA, intended for use in children. All three assays were assessed using 67 a panel of 1999 paired serum and oral fluids from children and adults participating in national primary 68 school SARS-CoV-2 surveillance studies during and after the first and second pandemic wave in the 69 UK. The anti NP IgG capture assay was the best candidate, with an overall sensitivity of 75% (95% 70 CI: 71–79%) specificity of 99% (95% CI: 78–99%) when compared with paired serum antibodies 71 measured using a commercial assay SARS-CoV-2 nucleoprotein IgG assay (Abbott, Chicago, IL, 72 USA). Higher sensitivity was observed in children (80%, 95% CI: 71–88%) compared to adults (67%, 73 CI: 60%-74%). Oral fluid assays using spike protein and RBD antigens were also 99% specific and 74 achieved reasonable but lower sensitivity in the target population (78%, 95% CI (68%-86%) and 53%, 75 95% CI (43%-64%), respectively). 76 Conclusion statement: 77 Oral Fluid assays based on the detection of SARS-CoV-2 antibodies are a suitable tool for population 78 based seroepidemiology studies in children. 79 All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted July 7, 2021. ; https://doi.org/10.1101/2021.07.07.21260121 doi: medRxiv preprint