An initial retrospective epidemiological investigation was conducted in a city north of France after the diagnosis of the first case of COVID-19 on February 2020. Sero-epidemiological studies were conducted in this town by the Institut Pasteur in early 2020 among families, teachers and non-teaching staff of the high and elementary schools.

The goal of this new project is to better characterize the specific immunity generated by the infection within this community. The specific immune response to the SARS-CoV-2 virus will be followed for a period of 2 years from the initial circulation of the virus, within a large cohort of participants covering all age groups from 5 years-old onwards. The study will focus on systemic humoral and cell responses, immunity of the nasopharyngeal mucosa and the humoral response present in saliva. Follow-up of participants in this cohort and monitoring of the virus circulation within this community would help to determine the protective character against re-infection of the natural immunity generated by SARS-CoV-2.

An initial retrospective epidemiological investigation was conducted in a city north of France after the diagnosis of the first case of COVID-19 on February 2020. Sero-epidemiological studies were conducted in this town by the Institut Pasteur in early 2020 among families, teachers and non-teaching staff of the high and elementary schools.

These surveys have documented the circulation of SARS-CoV-2 in one of the first French COVID-19 outbreaks and this study proposes to better characterize the specific immunity generated by the infection among this community. Indeed, the nature of this immunity and its persistence over time are crucial information. The goal of this new project is to explore the specific immune response to the SARS CoV 2 virus for a period of 2 years from the initial circulation of the virus in this north of France city, within a large cohort of participants in the general population covering all age groups from 5 years of age but also in patients and residents of retirement homes in this city. It is expected that the immune response conferred by natural infection or vaccination will differ according to age.

This study will focus on systemic humoral and cell responses, immunity of the nasopharyngeal mucosa and the humoral response present in saliva. The genetic basis of the diversity of humoral responses induced by SARS-CoV-2 and those related to the multiplicity of clinical manifestations of COVID-19 will also be investigated. This would provide initial evidence to determine the protective character against re-infection of the natural immunity generated by CoV-2-SARS. Finally, these data will be used to model the intra-family transmission of the virus.

Inclusion Criteria:

• Adultes and minors from 5 years old
• Affiliated with or benefiting from a Social Security system
• State of health compatible with a blood sample as defined in the protocol

Exclusion Criteria:

• Person benefiting from a legal protection measure or unable to express informed consent to participation and for which the legal representative or tutor person could not be contacted.

Pupils, their parents and siblings, as well as teachers and non-teaching staff of a high and elementary schools located in a city north of France.