Antibody status and cumulative incidence of SARS-CoV-2 infection among adults in three regions of France following the first lockdown and associated risk factors: a multicohort study

Abstract

Background We aimed to estimate the seropositivity to anti-SARS-CoV-2 antibodies in May–June 2020 after the first lockdown period in adults living in three regions in France and to identify the associated risk factors. Methods Between 4 May 2020 and 23 June 2020, 16 000 participants in a survey on COVID-19 from an existing consortium of three general adult population cohorts living in the Ile-de-France (IDF) or Grand Est (GE) (two regions with high rate of COVID-19) or in the Nouvelle-Aquitaine (NA) (with a low rate) were randomly selected to take a dried-blood spot for anti-SARS-CoV-2 antibodies assessment with three different serological methods (ClinicalTrial Identifier #NCT04392388). The primary outcome was a positive anti-SARS-CoV-2 ELISA IgG result against the spike protein of the virus (ELISA-S). Estimates were adjusted using sampling weights and post-stratification methods. Multiple imputation was used to infer the cumulative incidence of SARS-CoV-2 infection with adjustments for imperfect tests accuracies. Results The analysis included 14 628 participants, 983 with a positive ELISA-S. The weighted estimates of seropositivity and cumulative incidence were 10.0% [95% confidence interval (CI): 9.1%, 10.9%] and 11.4% (95% CI: 10.1%, 12.8%) in IDF, 9.0% (95% CI: 7.7%, 10.2%) and 9.8% (95% CI: 8.1%, 11.8%) in GE and 3.1% (95% CI: 2.4%, 3.7%) and 2.9% (95% CI: 2.1%, 3.8%) in NA, respectively. Seropositivity was higher in younger participants [odds ratio (OR) = 1.84 (95% CI: 1.79, 6.09) in <40 vs 50–60 years old and OR = 0.56 (95% CI: 0.42, 0.74) in ≥70 vs 50–60 years old)] and when at least one child or adolescent lived in the same household [OR = 1.30 (95% CI: 1.11, 1.53)] and was lower in smokers compared with non-smokers [OR = 0.71 (95% CI: 0.57, 0.49)]. Conclusions Seropositivity to anti-SARS-CoV-2 antibodies in the French adult population was ≤10% after the first wave. Modifiable and non-modifiable risk factors were identified.

Body weight, body composition and the risk of SARS‐CoV‐2 infection in a large population‐based sample

“…In men, most associations were non-significant (more limited sample size and power), except some inverse associations warranting further investigations, yet with a potential underlying mechanistic hypothesis involving reduced testosterone levels in obese men while testosterone would facilitate SARS-CoV-2 interaction with the angiotensin-converting enzyme 2 receptor [6]. The study strengths are the exhaustive seroprevalence assessment with highly sensitive assays (able to detect antibodies even in asymptomatic/mild cases) [5,7], independent of whether or not the participant sought testing in a large population-based sample with detailed phenotyping (including anthropometric data). Yet, there are some limitations: The imperfect sensitivity of the ELISA-S test [5,7] and a possible decrease in antibodies over time potentially resulting in some misclassification.…”

“…The study strengths are the exhaustive seroprevalence assessment with highly sensitive assays (able to detect antibodies even in asymptomatic/mild cases) [5,7], independent of whether or not the participant sought testing in a large population-based sample with detailed phenotyping (including anthropometric data). Yet, there are some limitations: The imperfect sensitivity of the ELISA-S test [5,7] and a possible decrease in antibodies over time potentially resulting in some misclassification. Waist and hip circumference data were collected in June 2020 and may be either post-, contemporary to or pre-SARS-CoV-2 infection (whereas most anthropometric data were collected before potential SARS-CoV-2 infection, allowing a prospective design: self-reported but validated [8] body weight measures, and measured body composition data but acquired long before the COVID-19 crisis), potentially resulting in some reverse causality bias if SARS-CoV-2 infection led to weight loss.…”

“…In June 2020, self-reported measures of current waist and hip circumference were provided following detailed instructions. Participants involved in the SAPRIS-SERO project returned self-sampled dried-blood spots in May-October 2020 that were analysed to detect anti-SARS-CoV-2 antibodies directed against the spike protein (ELISA-S) and the nucleocapsid protein (ELISA-NP), as well as neutralizing antibodies (SN) [5]. More details regarding the tests are provided in the Supporting Information.…”

“…More details regarding the tests are provided in the Supporting Information. The main outcome was a positive ELISA-S test, while being positive to all three ELISA-S, ELISA-NP and SN tests (likely to reflect more symptomatic forms of SARS-CoV-2 infection [5]) constituted the secondary outcome. Associations between the seroprevalence of SARS-CoV-2 and anthropometric characteristics were assessed using multi-adjusted logistic regression models (twosided tests, p < 0.05 considered as statistically significant; SAS 9.4).…”

Age, COVID-19-like symptoms and SARS-CoV-2 seropositivity profiles after the first wave of the pandemic in France

“…In France, SARS-CoV-2-positive RT-PCR tests were first reported on January 24, 2020 and an estimated 4-5% of the adult population in metropolitan France had developed antibodies against SARS-CoV-2 by May 2020 at the end of the first wave of the pandemic [2]. Our objective was to characterize the serological profile to different anti-SARS-CoV-2 antibodies in the general population in France after the first wave of the pandemic, to assess its dynamic over time as well as its association with the participants' characteristics and their past symptoms.…”