Prevalence of SARS-CoV-2 antibodies in France: results from nationwide serological surveillance
medRxiv (Cold Spring Harbor Laboratory)(2020)
Abstract
Background Assessment of cumulative incidence of SARS-CoV-2 infections is critical for monitoring the course and the extent of the epidemic. As asymptomatic or mild cases were typically not captured by surveillance data in France, we implemented nationwide serological surveillance. We present estimates for prevalence of anti-SARS-CoV-2 antibodies in the French population and the proportion of infected individuals who developed potentially protective neutralizing antibodies throughout the first epidemic wave.
Methods We performed serial cross-sectional sampling of residual sera over three periods: prior to (9-15 March), during (6-12 April) and following (11-17 May) a nationwide lockdown. Each sample was tested for anti-SARS-CoV-2 IgG antibodies targeting the Nucleoprotein and Spike using two Luciferase-Linked ImmunoSorbent Assays, and for neutralising antibodies using a pseudo-neutralisation assay. We fitted a general linear mixed model of seropositivity in a Bayesian framework to derive prevalence estimates stratified by age, sex and region.
Findings In total, sera from 11 021 individuals were analysed. Nationwide seroprevalence of SARS-CoV-2 antibodies was estimated at 0.41% [0.05−0.88] mid-March, 4.14% [3.31−4.99] mid-April and 4.93% [4.02−5.89] mid-May. Approximately 70% of seropositive individuals had detectable neutralising antibodies. Seroprevalence was higher in regions where circulation occurred earlier and was more intense. Seroprevalence was lowest in children under 10 years of age (2.72% [1.10−4.87]).
Interpretation Seroprevalence estimates confirm that the nationwide lockdown substantially curbed transmission and that the vast majority of the French population remains susceptible to SARS-CoV-2. Low seroprevalence in school age children suggests limited susceptibility and/or transmissibility in this age group. Our results show a clear picture of the progression of the first epidemic wave and provide a framework to inform the ongoing public health response as viral transmission is picking up again in France and globally.
Funding Santé publique France.
### Competing Interest Statement
The authors have declared no competing interest.
### Funding Statement
Santé publique France provided funding to the NRC and to the two centralising biobanks to cover sample collection, preparation, transport, and analysis costs. The funder had no role in analysis, interpretation of data or writing of the report. SLV, GJ and HN had full access to all the data and had responsibility to submit for publication.
### Author Declarations
I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.
Yes
The details of the IRB/oversight body that provided approval or exemption for the research described are given below:
Authorization for conservation and preparation of elements of the human body for scientific use was granted to the two biobanks by the bioethics committee from General Board for Research and Innovation (DGRI) of French Ministry of Higher Education and Research (approvals AC-2015-2418 and AC-2018-3329). Information regarding secondary use of de-identified residual sera for approved research studies was systematically displayed and orally communicated at the primary clinical laboratories. The Ethics Committee (Comité de Protection des Personnes Ile-de-France VI, CHU Pitié-Salpétrière Hospital, Paris, France) waived the need for ethical approval for the collection, analysis and publication of the retrospectively obtained and anonymized specimens and data for this study. This work was carried out following regulations of the French Public Health Code (articles L. 1413-7 and L. 1413-8) and the French Commission for Data Protection (CNIL).
All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived.
Yes
I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).
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I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.
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Data from the analysis can be made available upon request to the corresponding author and might require partial aggregation or downsampling to protect patient privacy.
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Key words
nationwide serological surveillance,sars-cov
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