The Coronavirus SARS CoV-2 (COVID-19) pandemic is causing a major global health crisis that is disrupting our hospital organizations and creating potential infectious risks for hospital staff on the front line when it comes to the support of infected people.

In this context, the Paris Saint-Joseph Hospital Group (GhPSJ) very early on wanted to implement an institutional approach aimed, on the one hand, at enabling each of its employees at its two sites (Hôpital Paris Saint-Joseph (HPSJ), Paris 14ème and Hôpital Marie Lannelongue (HML), Le Plessis Robinson, 92) to access their serological status with regard to SARS-CoV-2 and, on the other hand, to identify the risk factors for contracting COVID-19.

This collective approach consisted of an evaluation of its professional practices aimed at assessing the protective measures put in place to protect hospital personnel and identifying sources of potential improvement in the management of the infectious risk required to put in place in case of upcoming COVID-19 cases or any other epidemics in the future.

This institutional process had been validated by senior management and staff representative bodies. It was based on voluntary work, anonymity, the confidential aspect of the employees' analyses with the establishment of a follow-up and an individual counselling organized by the Occupational Health Service (SST) team and a team of COVID-19 Serology referents appointed to carry out and coordinate this process. Among the 3,600 GhPSJ employees, 3,062 (85%) samples were taken (and 404 employees from partner establishments in the hospital complex) for an initial serology test between April, 20th and May,15th and a second test one month later (M1) between May 18th and June 12th. The purpose of this second sampling was to get rid of the fear of another infection that might have occurred on the date of the first serology, and to observe the evolution between the two samples at the end of the epidemic phase.

The first results identified 310 people (231 from the HPSJ site and 56 from the HML site) (10.1%) with a positive serology for SARS CoV-2. However, it was observed that the people infected by the COVID-19, had highly variable IgG antibody titers and these titers changed unexpectedly. In fact, the majority of cases (89%) showed a drop in antibody titers as early as the first month and 20 of them (6.4%) even showed a negativation based on the index of quantitative ELISAs performed.

After only 5 months of hindsight in the face of this new pandemic, there are a few robust and specific data on the immune response following the COVID-19 and its involvement in the clinical impact on infected patients. In addition to the epidemiological interest and potential protection, the use of the immune response is an important therapeutic issue that is currently being evaluated, whether for passive immunization or primary prevention, with highly anticipated prospects for vaccination of populations.

It should be noted that the severely infected patients present characteristics unique to COVID-19 that are rarely seen in other respiratory viral infections, such as severe lymphopenia and eosinopenia, pneumonia and extensive lung damage, cytokine storm leading to acute respiratory distress syndrome and multisystem failure, and numerous atypical presentations (ENT, digestive, mucocutaneous, etc.). A high viral load at the time of first infection and/or repeated exposures to the virus, particularly for healthcare professionals, may be an important factor in the evolution of the disease (severe clinical forms, delayed clinical signs and particular serological kinetics).

In this context, the team in charge of coordinating the institutional project, in connection with the Occupational Health Service (SST) which followed all the personnel exposed during the epidemic period, wishes to propose to the GhPSJ personnel who desires a longitudinal follow-up as part of a research approach aimed at describing the kinetics of the antibodies produced following a COVID-19 infection and a medical follow-up including a self-questionnaire and a consultation specifically targeting the delayed clinical presentations after COVID-19 accompanied by a longitudinal serological follow-up over a longer period.

Inclusion Criteria:

• employee aged over 18 years
• employee who participated to the serology tests
• employee who was tested positively to the Covid-19 serology test
• French speaking employee
• employee affiliated to a French social security or any other health insurance system.
• employee who is able to give its free and written consent.

Exclusion Criteria:

• employee under guardianship or curatorship
• employee deprived of liberty
• employee under the protection of justice.