In early 2020, the first French death attributed to the SARS-CoV-2 virus was a teacher from Crépy-en-Valois, a city north of Paris. The intense circulation of the novel coronavirus in that area was confirmed by sero-epidemiological studies conducted by the Institut Pasteur among pupils, their families, teachers and non-teaching staffs (Fontanet et al.). Intense SARS-CoV-2 circulation during that period was also identified within the Crépy-en-Valois local hospital and nursing homes by diagnostic campaigns conducted by the Amiens hospital among residents and staffs (unpublished data).
The COVID-Oise project constitutes a unique opportunity to follow a general population cohort within an area that was one of the first affected in Europe in early 2020, in order to better characterize the immunity specific to the SARS-CoV-2 virus. The nature and duration of this immunity, whether acquired following natural infection and/or vaccination, and in the context of emerging variants of the virus, are key elements that will shape the future of the current pandemic.
The COVID-Oise cohort is constituted by participants across all age categories starting from 5 years-old, focusing on benign and asymptomatic COVID-19 forms that represent most of the clinical cases. Over a 2-year period, participants will be seen twice per year for clinico-epidemiological data collection and biological sampling. Several analyses will be run on the samples collected, including characterization of the SARS-CoV-2 specific humoral and cellular responses and immunity in the nasopharyngeal mucosa.
Status and preliminary results
At the end of 2020, hundreds of participants were enrolled in the cohort, including families from the Crépy-en-Valois area, staff and residents from the local hospital and nursing homes. Preliminary results confirm the high circulation of the SARS-CoV-2 virus within this population: more than 37% of the participants had detectable levels of anti-SARS-CoV-2 antibodies within their serum at the end of 2020 (32% of the participants included among families, 44% of the hospital staff and 72% of the nursing home residents). Most of the enrolled families already participated in the sero-epidemiological studies conducted in early 2020, allowing for a monitoring starting from the initial identification of SARS-CoV-2 circulation in that area. More than 90% of those that had detectable anti-SARS-CoV-2 antibodies in early 2020 remained seropositive 8 months later at the end of 2020.
Follow-up visits are scheduled for spring 2021, autumn 2021 and spring 2022. Additional participants will also be invited to join the cohort during each session.
Beyond the longitudinal follow-up goal of the COVID-Oise cohort, samples collected in the framework of the initial sero-epidemiological studies conducted in Crépy-en-Valois in early 2020 contributed to several advances and findings:
– At a time when serological tests were not yet commercialized, serological assays were established by several teams within the Institut Pasteur based on sera from infected individuals (Grzelak et al.).
– In-depth analysis of antibody functions in sera from infected individuals showed that asymptomatic SARS-CoV-2 infection elicits polyfunctional antibodies neutralizing the virus and targeting infected cells through complement deposition and antibody-dependent cellular toxicity, but to a lower degree than symptomatic infection (Dufloo et al.).
– Quantitative measurements of antibodies of different isotypes against several SARS-CoV-2 antigens within sera of infected individuals allowed accurate classification of time since infection into intervals of 0-3 months, 3-6 months, 6-12 months using machine learning algorithms. The ensuing computational method could be used to reconstruct past SARS-CoV-2 transmission when applied to samples from a single cross-sectional sero-prevalence survey (Pelleau et al.).
Institut Pasteur: Medical research direction, Center for translational research, Clinical investigation and biological resources platform
CHU Amiens: Biology-pharmacy department
– Fontanet A, et al. SARS-CoV-2 infection in schools in a northern French city: a retrospective serological cohort study in an area of high transmission, France, January to April 2020. Euro Surveill. 2021 Apr;26(15). doi: 10.2807/1560-7917.ES.2021.26.15.2001695. PMID: 33860747.
– Grzelak L, et al. A comparison of four serological assays for detecting anti-SARS-CoV-2 antibodies in human serum samples from different populations. Sci Transl Med. 2020 Sep 2;12(559):eabc3103. doi: 10.1126/scitranslmed.abc3103. Epub 2020 Aug 17. PMID: 32817357; PMCID: PMC7665313.
– Dufloo J, et al. Asymptomatic and symptomatic SARS-CoV-2 infections elicit polyfunctional antibodies., Cell Reports Medicine (2021), doi:https://doi.org/10.1016/j.xcrm.2021.100275.
– Pelleau S, et al. Serological reconstruction of COVID-19 epidemics through analysis of antibody kinetics to SARS-CoV-2 proteins. medRxiv (2021), doi: https://doi.org/10.1101/2021.03.04.21252532.