The main objective of the study is to describe the temporal curve of COVID-19 IgG and neutralizing antibodies over 24 months in an identified population of patients who presented with SARS-CoV-2 virus infection. The secondary objectives are to characterize the kinetics of the antibodies according to the severity of the clinical presentation and patient's characteristics and to determine if the anti-SARS-CoV-2 antibodies retain their neutralizing capacity over time. A sub-study aims to describe the kinetic of neutralizing antibodies (in blood and nasal mucosa) after vaccination.

Given the seriousness of the global health consequences of the COVID-19 pandemic and the difficulty of covering the world population with effective vaccination, several questions arise:

• Are the antibodies made by a patient neutralizing and do they protect the individual from further contamination?
• What is the persistence of the antibodies over time according to the clinical presentation, knowing that the very symptomatic forms have developed a much higher level of antibodies than the forms followed only on an outpatient basis and no less severe?
• What is the impact of vaccination (against wild-type virus and emerging variants) ? The investigators propose a single-center, observational study including 300 patients to answer the two questions, by selecting from the file of all the patients having had a positive RT-PCR 3 distinct groups: severe (hospitalized), pauci-symptomatic to moderate (followed in ambulatory only). Note: people living with HIV can be included in each of the groups.

MAIN EVALUATION

> Presence of specific anti-SARS-CoV-2 antibodies in the different study groups at M24 at each of the sampling times (M0, M3, M6, M9, M12, M15, M18, M24)

SECONDARY EVALUATION CRITERIA

• Presence of specific anti-SARS-CoV-2 antibodies in the different groups of the study at M12 and in each of the subgroups at M12 and M24
• Neutralizing capacity of anti-SARS-CoV-2 antibodies to M6, M12 and M24 on the classical strain and the new variants, before and after a possible vaccination against COVID-19
• Measurement of CD8 (CD38 + DR +), CD4 and activated B lymphocytes in culture This will make it possible to answer the question of the persistence or not of an immune response over 24 months, an essential element in the event of seasonal circulation of the virus in the years to come, and of the persistence or not of the neutralizing capacities of these antibodies in the over time, especially when the title approaches the detection threshold.

These information will be decisive in the event of successive waves of the SARS-CoV-2 epidemic given a low level of collective immunity (<10% in France at the end of 2020) in order to know whether previously affected patients are durably protected.

In the context of a lack of vaccine, results from this study would make it possible to select candidates for vaccination from the truly non-immune population.

Vaccine sub-study :

Study of the kinetic of neutralizing antibodies after vaccination :

Volunteers participants, provided they give a special agreement for the vaccine sub-study, will undergo an additional grid of samples to accurately study the kinetic of neutralizing antibodies before and monthly after (up to 6 months) receiving anti-SARS-CoV-2 vaccine (whatever the product used). A special attention will be given to the capacity of their antibodies to neutralize emerging variants. Samples will include blood and possibly nasopharyngeal swabs (not mandatory).

Inclusion Criteria:

• Age > 18
• Having had a confirmed infection with CoV-2-SARS by RT-PCR and/or serology (IgM and/or IgG specific as significant)
• Being vaccinated against anti-SARS-CoV-2 (vaccine sub-study)
• Benefiting from a Social Security system
• Having consented to participate in the study
• Accepting regular follow-up for 24 months

Exclusion Criteria:

• Protected person (under guardianship or trusteeship)
• Person under the protection of justice
• Person unable to express consent