Table 5. Description of Serological Tests in Included Studies Conducted in Close Contact Settings.

Study ID	Serological test	Description of test	Thresholds for serological positivity
Agergaard 2020	IgG and IgM	iFlash and DiaSorin	iFlash SARS-CoV-2 N/S IgM/IgG cut-off: ≥12 AU/ml = positive. DiaSorin SARS-CoV-2 S1/S2 IgG cut-off: ≥15 AU/ml = positive, 12 < x < 15 AU/ml = equivocal, and ≤12 AU/ml = negative.
Angulo-Bazán 2021	IgG and IgM	Coretests ® COVID-19 IgM / IgG Ab Test (Core Technology Co. Ltd), a lateral flow immunochromatographic test that qualitatively detects the presence of antibodies against SARS-CoV-2, with a sensitivity and specificity reported by the manufacturer for IgM / IgG of 97.6% and 100%, respectively	Not reported
Armann 2021	IgG	Diasorin LIAISON® SARS-CoV-2 S1/S2 IgG Assay). All samples with a positive or equivocal LIAISON® test result, as well as all samples from participants with a reported personal or household history of a SARS-CoV-2 infection, were re-tested with two additional serological tests: These were a chemiluminescent microparticle immunoassay (CMIA) intended for the qualitative detection of IgG antibodies to the nucleocapsid protein of SARS-CoV-2 (Abbott Diagnostics® ARCHITECT SARS-CoV-2 IgG ) (an index (S/C) of < 1.4 was considered negative whereas one >/= 1.4 was considered positive) and an ELISA detecting IgG against the S1 domain of the SARS-CoV-2 spike protein (Euroimmun® Anti-SARS-CoV-2 ELISA) (a ratio < 0.8 was considered negative, 0.8–1.1 equivocal, > 1.1 positive) Participants whose positive or equivocal LIAISON® test result could be confirmed by a positive test result in at least one additional serological test were considered having antibodies against SARS-CoV2.	Antibody levels > 15.0 AU/ml were considered positive and levels between 12.0 and 15.0 AU/ml were considered equivocal.
Baettig 2020	IgG and IgM	Used commercially available immunochromatography rapid test with SARS-CoV-2 protein-specific IgM and IgG. This test was performed according to the manufacturers’ instructions with a reported sensitivity and specificity of 93% and 95%, respectively.	Not reported
Basso 2020	IgG and IgM	Sera were collected approximately 3 weeks following exposure for the detection of antibodies against SARS-CoV-2. EDI Novel Coronavirus COVID-19 lgG and IgM ELISA (Epitope Diagnostics, Inc., San Diego, CA, USA) were used for initial testing, and supplemented with tests from DiaSorin (LIAISON SARS-CoV-2 S1/S2 IgG test), Abbott (Alinity i SARS-CoV-2 IgG), Roche (Elecsys Anti-SARS-CoV-2) and Wantai (WANTAI SARS-CoV-2 Ab ELISA).	Not reported
Bernardes- Souza 2021	IgM or IgG	Participant’s peripheral blood (3 mL) was collected by puncture of the brachiocephalic vein by a trained nurse and then transferred to a serum-separating tube. The tube was stored between 2 °C to 8 °C and transported within 2 hours to the public laboratory of the town Department of Health, where it was immediately centrifuged (2000xg for 10 minutes) and the separate serum was tested for SARS- CoV-2 antibodies using a lateral flow immunoassay according to the manufacturer’s instructions.	The sample was considered positive if IgM or IgG antibodies were detectable.
Bhatt 2022	IgG, IgA or IgM	ELISA adapted and optimized from the assay were used to evaluate SARS-CoV-2-specific IgA, IgM and IgG against the spike-trimer and nucleocapsid protein.	Samples were considered antibody positive for a particular isotype (IgG, IgA or IgM) when both antispike and anti- nucleocapsid antibodies were detected above the cut-off values (signal-to-cut- off value ≥ 1) for that isotype. Samples were considered positive for SARS-CoV- 2 antibody if they were positive for IgG or for both IgA and IgM.
Bi 2021	IgG	ELISA targeting the S1 domain of the spike protein of SARS-CoV-2; sera diluted 1:101 were processed on a EuroLabWorkstation ELISA.	Seropositivity was defined based on the cutoff recommended by the manufacturer and explored a higher cut- off of 1.5 (>1.5) in sensitivity analyses.
Brown 2020	IgG and IgM	ELISA (authors referenced another study)	Reciprocal titers of >400 to be positive and reciprocal titers of >100 but <400 to be indeterminate.
Chen 2020b	IgG and IgM	In-house enzyme immunoassay (EIA). 96-well plates were coated with 500 ng/mL of recombinant RBD or NP protein overnight, incubating with diluted serum samples at 1:20. Plates were incubated with either anti-human IgM or IgG conjugated with HRP. Optical density (OD) value (450nm-620nm) was measured.	Preliminary cut-off values were calculated as the mean of the negative serum OD values plus 3 standard deviations (SD) from 90 archived healthy individuals in 2019. A close contact was considered seropositive if OD of 1:20 diluted serum was above the cut-off values for either IgM or IgG against both RBD and NP protein
Chu 2020	IgG and IgM	Serum samples were tested at CDC using a SARS-CoV-2 ELISA with a recombinant SARS-CoV-2 spike protein (courtesy of Dr. Barney Graham, National Institutes of Health, Bethesda, MD, USA) as an antigen. Protein ELISA 96-well plates were coated with 0.15 μg/mL of recombinant SARS-CoV-2 spike protein and ELISA was carried out as previously described. An optimal cutoff optical density value of 0.4 was determined for >99% specificity and 96% sensitivity. Serum samples from the case-patient were used as a positive control and commercially available serum collected before January 2020 from an uninfected person as a negative control.	Total SARS-CoV-2 antibody titers >400 was considered seropositive.
Craxford 2021	IgG	ELISA. Serum samples were serially diluted in 3% skimmed milk powder in PBS containing 0.05% Tween 20 and 0.05% sodium azide. All assays were performed on Biotek Precision liquid handling robots in a class II microbiological safety cabinet. For endpoint dilution ELISAs, sera were progressively 4-fold diluted from 1:150 to 1;38,400.	Participants found to be seropositive for SARS-CoV-2 were assessed for the presence of neutralising antibodies.
Dattner 2020	IgG	Abbott SARS-CoV-2 IgG, whose specificity was estimated as ∼100% and whose sensitivity at ≥ 21 days was estimated as ∼85%	Not reported
de Brito 2020	IgG and IgM	Chemiluminescence 4 weeks after contact with the index case	Not reported
Dimcheff 2020	IgG	Serum IgG to thD4:D12e nucleoprotein of SARS-CoV-2 was measured using a Federal Food and Drug Administration (FDA) emergency-use–authorized chemiluminescent microparticle immunoassay performed on an automated high throughput chemistry immunoanalyzer (Architect i2000SR, Abbott Laboratories, Abbott Park, IL). The sensitivity of this assay is reported to be 100% with a specificity of 99% at >14 days after symptom onset in those infected with SARS-CoV-2.1 At 5% prevalence, the positive predictive value is 93.4% and the negative predictive value is 100%	Results are reported in a relative light units (RLU) index; a value ≥1.4 RLU is considered a positive antibody response.
Dub 2020	IgG	IgG antibodies to SARS-CoV-2 nucleoprotein (The Native Antigen Company, United Kingdom) were measured with a fluorescent bead-based immunoassay (manuscript in preparation). Antigen was conjugated on MagPlex Microspheres and bound IgG antibodies were identified by a fluorescently labeled conjugated antibody (RPhycoerythrin-conjugated Goat Anti-Human IgG, Jackson Immuno Research, USA). The plate was read on Luminex® MAGPIX® system. xPONENT software version 4.2 (Luminex®Corporation, Austin, TX) was used to acquire and analyze data. Median fluorescent intensity was converted to U/ml by interpolation from a 5- parameter logistic standard curve. The specificity and sensitivity of the assay was assessed using receiver operator curve (ROC) with 100% specificity and 97.9% sensitivity	MNT titre of ≥ 6 considered positive FMIA titre 3·4 U/ml considered positive
Farronato 2021	IgM or IgG	Rapid lateral flow chromatographic test. If the test sample contains IgM or IgG antibodies to SARS- CoV-2, the test displays two different visible bands (test line and control line); however, if these antibodies are absent, only the control line appears.	Participants found to be seropositive for SARS-CoV-2 were assessed for the presence of neutralising antibodies.
Fontanet 2021	IgG	ELISA N assay, detecting antibodies binding to the nucleocapsid (N) protein; a S-Flow assay, which is a flow-cytometry based assay detecting anti-spike (S) IgG; and a luciferase immunoprecipitation system (LIPS) assay, which is an immunoprecipitation-based assay detecting anti-N, anti-S1 and anti-S2 IgG. Samples were also tested for neutralisation activity using a viral pseudotype-based assay.	In the high school study, participants were considered seropositive for SARS-CoV-2 antibodies if any of the serological assay tests were positive.
Galow 2021	IgG	SARS-CoV-2 IgG antibodies were detected via Diasorin LIAISON® SARS-CoV-2 S1/S2 IgG Assay and positive or equivocal results were confirmed via Abbott Diagnostics® ARCHITECT SARS-CoV-2 and Euroimmun® Anti-SARS-CoV-2 ELISA.	Participants whose positive or equivocal LIAISON® test result could be confirmed by an additional serological test were considered seropositive for SARS-CoV-2.
Gaskell 2021	IgG	Serum samples were analysed for the presence of IgG specific for SARS CoV-2 trimeric spike protein (S), Receptor Binding Domain (RBD) and nucleocapsid (N) antigens using a multiplex chemiluminescence immunoassay.	Not reported
Gomaa 2021	Unclear	Microneutralization Assay was conducted to measure the nAb titre in human sera using Vero-E6 (ATCC, CRL-1586) cell monolayers using SARS-CoV-2/Egypt/NRC-03/2020 under biological safety level 3. The plates were then incubated for three more days at 37°C in 5% CO2 in a humidified incubator. A virus back-titration was performed without immune serum to confirm TCID50 viral titre used. Cytopathic effect (CPE) was observed post 72 hrs of infection.	The reciprocal of the serum dilution that protected cells from CPE was considered the nAb titre. Negative sera were given a value of 1:5.
Gonçalves 2021	IgM or IgG	Seropositivity was determined by a point-of-care rapid antibody test. The assays were carried out according to the manufacturers protocol: a 10 μl sample (whole blood or serum) was applied to the sample well, followed by the addition of 2-3 drops or 80μl of diluent. The test was developed for 15 minutes at room temperature and the results (positive or negative) were read by independent experienced readers blinded to the sample status.	Control line threshold
Gu 2020	IgG	Not described	Not reported
Helsingen 2020	IgG	Measurement of IgG antibodies was performed with a multiplex flow cytometric assay known as microsphere affinity proteomics (MAP)	Not specified. Referenced
Hong 2020	IgG and IgM	Qualitative colloidal gold assay (Innovita (Tangshan) Biological Technology, Co., Ltd, Tangshan, China), following manufacturers’ instructions. The sensitivity of the assay was 87.3% (95%CI 80.4–92.0%), and the specificity was 100% (95%CI 94.20–100%) according to the instructions of the assay.	Not reported
Jeewandara 2021	Unclear	Due to the limitations in using a BSL-3 facility to carry out assays to measure neutralizing antibodies, the Nabs were measured using a surrogate virus neutralization test (sVNT). ELISA was used to assess antibody responses.	Inhibition percentage ≥ 25% in a sample was considered as positive for Nabs.
Jordan 2022	IgG	Not reported	Not reported
Katlama 2022	IgM or IgG	ach index case and all contact individuals were tested using the rapid immunochromatographic lateral flow assay (LFA) COVID-PRESTO manufactured by AAZ detecting total SARS-CoV-2 IgG, IgM, or both antibodies targeting the N-protein with a sensitivity of 78.4% and 92.0% and a specificity of 100% and 92% for IgM and IgG. The presence of IgG antibodies against the nucleocapsid protein was measured and interpreted using commercially available chemiluminescent microparticle immunoassay (CMIA) kits.	Not specified
Kim 2021	IgM or IgG	IgM and IgG and ELISA total antibody testing. The FIA IgM and IgG kit used the automated fluorescent lateral flow immunoassay method, using the AFIAS-6 analyzer system.	FIA kit Specimens with a relative cut-off index (COI) value ≥ 1.1 were considered positive. ELISA: An optical density (OD) ratio < 1.0 was interpreted as negative, ≥0.9 to <1.0 as borderline, and ≥1.0 as positive.
Kolodziej 2022	IgG	Sera were tested for the presence of immunoglobulin G antibodies reactive with the SARS-CoV-2 spike trimer, S1, and N antigens in a protein microarray, in duplicate 2-fold serial dilutions starting at 1:20. For each antigen, a 4-parameter log logistic calibration curve was generated and effective concentration 50, mid-point antibody titres were calculated.	Not specified
Kuwelker 2020	IgG	A two-step ELISA was used for detecting SARS-CoV-2-specific antibodies, initially by screening with receptor-binding domain (RBD) and then confirming seropositivity by spike IgG. Endpoint titres were calculated as the reciprocal of the serum dilution giving an optical density (OD) value=3 standard deviations above the mean of historical pre-pandemic serum samples. Individuals with no antibodies were assigned a titre of 50 for calculation purposes. Neutralisation assays were used to quantify SARS-CoV-2-specific functional antibodies. VN titres were determined as the reciprocal of the highest serum dilution giving no CPE. Negative titres (<20) were assigned a value of 10 for calculation purpose.	Not specified.
Kuwelker 2021	IgG	A two-step ELISA was used for detecting SARS-CoV-2-specific antibodies, initially by screening with receptor-binding domain (RBD) and then confirming seropositivity by spike IgG. The neutralisation assays were used to quantify SARS-CoV-2-specific functional antibodies.	ELISA: Individuals with titres ≥100 were defined as positive and those with no antibodies were assigned a titre of 50 for calculation purposes. Neutralisation assays: Negative titres (<20) were assigned a value of 10 for calculation purpose.
Lewis 2020	Not specified	ELISA (authors referenced another study)	Not specified
Lin 2021	IgM or IgG	SARS-CoV-2 IgM and IgG antibodies were detected by Chemiluminescence and GICA. The test results were expressed in relative light units (RLU), and the IgM or IgG levels were positively correlated with RLU. The instrument automatically calculated IgM or IgG antibody levels (AU/mL) based on RLU and the built-in calibration curve.	Test result ≥ 10.0 AU/mL was reported as positive.
Luo 2020a	IgG and IgM	Not described	Asymptomatic: Specific IgM detected in serum. Symptomatic: Detectable SARS-CoV- 2–specific IgM and IgG in serum, or at least a 4-fold increase in IgG between paired acute and convalescent sera.
Macartney 2020	IgA, IgG, IgM	SARS-CoV-2-specific IgG, IgA, and IgM detection was done using an indirect immunofluorescence assay (IFA) that has a sensitivity compared with nucleic acid testing of detecting any of SARS-CoV-2- specific IgG, IgA, or IgM when samples were collected at least 14 days after illness onset of 91·3% (95% CI 84·9–95·6) and specificity of 98·9% (95% CI 98·4–99·3%; MVNO, personal communication).	Not specified
Martinez- Fierro 2020	IgG and IgM	IgM and IgG against SARS-CoV-2 were determined using a total blood sample through a 2019 nCov IgG/IgM rapid test (Genrui Biotech, Shenzen, China)	Not specified
Mercado- Reyes 2022	IgM or IgG	Prior infection by SARS-CoV2 was ascertained by measuring total antibodies (IgM+ IgG) using the SARS-CoV-2 Total (COV2T) Advia Centaur – Siemens chemiluminescent immunoassay (CLIA). Sera from 149 patients with SARS-CoV-2 infection, confirmed by RT-PCR and obtained less than 14 days after the onset of symptoms, were used as positive controls.	Not specified
Meylan 2021	IgG	Serum samples were analysed for SARS-CoV-2 serology (IgG), using a previously described Luminex- based assay quantifying antibody binding to the trimeric form of the SARS-CoV-2 S-protein.	This assay has shown a sensitivity and specificity of 97% and 98%, respectively, on hospitalised patients for the chosen cut-off of positivity defined at a ratio >5.90.
Miller 2021	IgG	Blood samples were tested for IgG antibody to the nucleocapsid protein (NP) by a commercial NP assay and also by an in-house ELISA that used the receptor binding domain (RBD) as antigen.	The cut-off for antibody positivity used in the analyses were ≥0.8 for the Abbott assay and ≥5.0 for the RBD ELISA.
Ng 2020	Not specified	human ACE-2 (hACE2) protein (Genscript Biotech, New Jersey, United States) was coated at 100 ng/well in 100 mM carbonate-bicarbonate coating buffer (pH 9.6). 3ng of horseradish peroxidase (HRP)-conjugated recombinant receptor binding domain (RBD) from the spike protein of SARS-CoV- 2 (GenScript Biotech) was pre-incubated with test serum at the final dilution of 1:20 for 1 hour at 37°C, followed by hACE2 incubation for 1 h at room temperature. Serum samples were tested with a surrogate viral neutralising assay for detection of neutralising antibodies to SARS-CoV-2.	A positive serological test result was concluded if the surrogate viral neutralising assay for a particular sample resulted in inhibition of 30% or greater (98·9% sensitivity and 100·0% specificity)
Ogawa 2020	IgG	Abbott ® (Abbott ARCHITECT SARS-CoV-2 IgG test, Illinois, USA)	Not specified
Petersen 2021	Unclear	SARS-CoV-2 Ab ELISA kit was used to determine serologic status	Not specified
Poletti 2020	IgG	Not described	Not specified
Powell 2022	Unclear	Oral fluid (OF) swabs tested for antibodies against the SARS-CoV-2 Nucleoprotein using an Immunoglobulin G capture-based enzyme immunoassay.	Not specified
Ratovoson 2022	IgM or IgG	ELISA for the detection of total antibodies (including IgM and IgG) to SARS-CoV-2.	Not specified
Razvi 2020	IgG and IgM	Blood samples were analysed on the day of collection using the Roche Elecsys Anti-Sars-CoV-2 serology assay. This electro chemiluminescent immunoassay is designed to detect both IgM and IgG antibodies to SARS-CoV-2 in human serum and plasma and has been shown to have a high sensitivity and specificity	Not specified
Reukers 2021	IgM or IgG	ELISA for the detection of total antibodies (including IgM and IgG) to SARS-CoV-2.	Not specified
Satter 2022	IgM or IgG	ELISA for the detection of total antibodies (including IgM and IgG) to SARS-CoV-2. The Receptor Binding Domain (RBD) of the spike protein of SARS-CoV-2 was used as an antigen to detect antibody responses	Using serum from pre-pandemic healthy controls, the concentration of 500 ng/mL (0.5 µg/mL) was determined as a cut-off value for seropositivity for both RBD-specific IgG and IgM antibodies.
Schumacher 2020	IgG and IgM	SARS-CoV-2-specific antibodies were measured in serum samples using an electrochemiluminescence immunoassay (Elecsys® Anti-SARS-CoV-2, Roche Diagnostics, Rotkreuz, Switzerland).	Cut-off indices ≤1 reported as negative and indices >1 as positive.
Sordo 2022	IgG	Not reported	4-fold or greater increase in a SARS-CoV-2 antibody of any subclass.
Stich 2021	IgM or IgG	ELISA for the detection of total antibodies (including IgM and IgG) to SARS-CoV-2. Antibodies reactive to the N protein were measured either with the Elecsys Anti-SARS-CoV-2 IgG/IgM ECLIA test kit. Neutralisation assays were performed.	Serum samples with a positive reaction in the additional assay were classified as seropositive.
Tadesse 2021	IgM or IgG	ELISA for the detection of total antibodies (including IgM and IgG) to SARS-CoV-2. Chemiluminescent microparticle immunoassay (CMIA) was used to determine seroprevalence.	Not specified
Torres 2020	IgG and IgM	Novel Coronavirus (2019-nCoV) IgG/IgM Test Kit (Colloidal gold) from Genrui Biotech Inc. The study nurse and/or technician viewed the photo provided by the participant along with the participant’s self-report as to the visibility of the three bands, and determined whether the tests were IgG+, IgM+, IgG & IgM+, Negative, Invalid, or Indeterminate. Participants were asked to attach a photo of the test after 15 minutes had elapsed and self-report the appearance of the three lines, G (IgG), M (IgM), and C (test control)	Colour-coded - self-administered test: self-reporting the appearance of the three lines, G (IgG), M (IgM), and C (test control)
van der Hoek 2020	IgG	Fluorescent bead-based multiplex-immunoassay. Referenced	A cut-off concentration for seropositivity (2.37 AU/mL; with specificity of 99% and sensitivity of 84.4%) was determined by ROC-analysis of 400 pre-pandemic control samples
Wendt 2020	IgA and IgG	ELISA (Euroimmun, Lübeck, Germany), following the manufacturer’s instructions.	Inconclusive (≥0.8 and <1.1) or Positive (≥1.1
Wiens 2021	IgG	ELISA for IgG antibodies. This assay quantifies RBD-specific antibody concentrations (μg/mL) using IgG-specific anti-RBD monoclonal antibodies. To help decide on an appropriate positivity threshold and assess assay specificity, the authors measured background antibody reactivity using 104 dried blood spot samples collected in Juba in 2015.	Seropositivity threshold (0.32 μg/mL) that corresponded to 100% specificity in these pre-pandemic samples (i.e., their highest value) and 99.7% in the pre-pandemic samples collected from the USA.
Yang 2020	IgA, IgG, IgM	Serum immunoglobulin (Ig) antibody against the SARS-CoV-2 surface spike protein receptor-binding domain (RBD) was measured using a chemiluminescence kit (IgM, IgG, and total antibody, Beijing Wantai Biotech, measured by cut-off index [COI]) or ELISA kit (IgA, Beijing Hotgen Biotech, measured by optical density at 450/630 nm [OD450/630]). The cut-off for seropositivity was set according to the manufacturer’s instruction, verified using positive (169 serum specimens from confirmed COVID-19 patients) and negative (128 serum specimens from healthy persons) controls, and both of sensitivity and specificity were 100%. Virus neutralization assays were performed using SARS-CoV-2 virus strain 20SF014/vero-E6/3 (GISAID accession number EPI_ISL_403934) in biosafety level 3 (BSL-3) laboratories. Neutralizing antibody (NAb) titer was the highest dilution with 50% inhibition of cytopathic effect, and a NAb titer of ≥1:4 was considered positive.	Specimens with COI>1 (IgM, IgG, or total antibody), OD450/630 > 0.3 (IgA) were considered positive.
Zhang 2020b	IgG and IgM	SARS-CoV-2-specific IgM and IgG were tested by paramagnetic particle chemiluminescent immunoassay using iFlash-SARS-CoV-2 IgM/IgG assay kit (Shenzhen YHLO Biotech Co., Ltd) and iFlash Immunoassay Analyzer (Shenzhen YHLO Biotech Co., Ltd). The specificity and sensitivity of SARS-CoV-2 IgM and IgG detection were also evaluated	Not specified