The objective of the COVID-HOP study is to identify biological and non-biological markers associated to: a positive or negative serology anti SRAS-Cov-2; a positive serology and having presented symptoms or, on the contrary, not having had symptoms; the persistence of immunity or the loss of this immunity over time; the protective nature of the presence of anti SRAS-Cov-2 antibodies.

To answer these questions, a biological collection (serum, plasma, DNA, RNA, mono-nucleated cells and urine) and a collection of detailed clinical data during the serological screening for SARS-CoV-2 of hospital agents (medical and non-medical staff) of the Assistance Publique Hôpitaux de Paris (Paris, France) will be carried out. 4000 professionals in 5 hospitals will be included. As part of the research, the anti SRAS-CoV-2 serology will be monitored 6 months and 12 months after the initial serology. Numerous studies will be carried out from this biological collection and from the database to answer the primary and secondary endpoints.

To answer the questions raised in the primary and secondary endpoints, a biological collection (serum, plasma, DNA, RNA, mono-nucleated cells and urine) and a collection of detailed data by the mean of a questionnaire (demographic, clinical, lifestyle, professional exposure to the virus, COVID-19 infection with detailed symptoms and complications) during the serological screening for SARS-CoV-2 of hospital agents (medical and non-medical staff) of the Assistance Publique Hôpitaux de Paris (Paris, France) will be carried out. 4000 professionals in 5 hospitals of the Assistance Publique Hôpitaux de Paris. As part of the research, the anti SRAS-CoV-2 serology will be monitored 6 months (M6) and 12 months (M12) after the initial serology and a brief questionnaire (update regarding treatments, co-morbidities, and COVID-19 infection) will be fulfilled at these two time points. Of note, if the inclusion could not be performed during the initial serological screening, the professional will be recalled to be included at M6.

Statistical analysis: The analysis of the determinants independently associated with symptomatic COVID + status will be carried out by uni- and multivariate logistic regression. The internal validation will be carried out by methods of draw with discount (bootstrap). The performance of the model will include calibration (graphical method) and discrimination (AUC). The biomarker study will include the study of the association with COVID + symptomatic versus asymptomatic status by univariate then multivariate analyzes (logistic regression) including clinical variables. The additional value of biomarkers will be studied by comparing the discriminating power of clinical models with and without the new biomarker. Finally, the study of the heterogeneity of COVID + symptomatic and asymptomatic patients will be carried out by an unsupervised analysis of Machine Learning known as archetypes.

Inclusion Criteria:

• Hospital staff (medical and non-medical)
• Age greater than or equal to 18 years
• Benefiting from or having benefited 6 months ago from carrying out a SARS-CoV-2 serology by venous sampling on a APHP site as part of monitoring by a screening center
• Having been informed about the study and having given their informed consent to participate in the study
• Beneficiary or entitled to a social security scheme

Exclusion Criteria:

• Refusal to participate in the study
• Previously known anemia with hemoglobin <10 g / dL
• Subject already included in a cohort study with biological collection COVID-19
• Exclusion period for subjects included or having been included in a COVID-19 interventional study (prophylactic or curative) or other clinical study
• Subject who received blinded treatment for SARS-Cov-2 in a clinical study
• Recent COVID-19 compatible infection with D0 of symptoms less than 4 weeks before collection
• Subject subject to a judicial protection measure
• Subject under guardianship or curatorship
• Subject under state medical aid

Hospital staff agent (medical and non medical) from the "Assistance Publique Hôpitaux de Paris" undergoing a serology to depict IgG anti SRAS-Cov-2 antibodies in a screening center from the "Assistance Publique Hôpitaux de Paris" .

from february 2021 for the primary outcome and as long as samples will be available in the biological collection.

Ancillary studies willing to use the biological collection and/or dataset of the COVID-HOP study will be submitted to the scientific board of COVID-HOP for evaluation.

Data sharing must be accepted by the sponsor and the PI based on scientific project and scientific involvement of the PI team.

Teams wishing obtain IPD must meet the sponsor and IP team to present scientifics (and commercial) purpose, IPD needed, format of data transmission, and timeframe. Technical feasibility and financial support will be discussed before mandatory contractualization