Seroprevalence of SARS-CoV-2, Symptom Profiles and Sero-Neutralization in a Suburban Area, France

Abstract

The World Health Organisation recommends monitoring the circulation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We investigated anti–SARS-CoV-2 total immunoglobulin (IgT) antibody seroprevalence and in vitro sero-neutralization in Nancy, France, in spring 2020. Individuals were randomly sampled from electoral lists and invited with household members over 5 years old to be tested for anti–SARS-CoV-2 (IgT, i.e., IgA/IgG/IgM) antibodies by ELISA (Bio-rad); the sero-neutralization activity was evaluated on Vero CCL-81 cells. Among 2006 individuals, the raw seroprevalence was 2.1% (95% confidence interval 1.5 to 2.9), was highest for 20- to 34-year-old participants (4.7% (2.3 to 8.4)), within than out of socially deprived area (2.5% vs. 1%, p = 0.02) and with than without intra-family infection (p < 10−6). Moreover, 25% of participants presented at least one COVID-19 symptom associated with SARS-CoV-2 positivity (p < 10−13), with highly discriminant anosmia or ageusia (odds ratio 27.8 [13.9 to 54.5]); 16.3% (6.8 to 30.7) of seropositive individuals were asymptomatic. Positive sero-neutralization was demonstrated in vitro for 31/43 seropositive subjects. Regarding the very low seroprevalence, a preventive effect of the lockdown in March 2020 can be assumed for the summer, but a second COVID-19 wave, as expected, could be subsequently observed in this poorly immunized population.

SARS-CoV-2 seroprevalence in healthcare workers and risk factors

“…Locally, another study evaluated the seroprevalence in laboratory staff of the same university hospital. This one was almost equal to that of local general population ( 5 , 7 ) and lower compared to HCWs. When handling samples, laboratory technicians are better protected than HCWs, in particular through the use of microbiological safety stations in addition to PPE ( 7 ).…”

“…SARS-CoV-2 seroprevalence of Nancy University Hospital HCW (5.1%) was lower than that in the Whole Northeast of France (6.7%) but higher to that of the Nancy Town (2.1 %) metropolis ( 5 ). Yet, seroprevalence was not associated with working in a COVID-19 unit.…”

Asymptomatic SARS-CoV-2 infections tend to occur less frequently in developed nations

“…We ensured a sample size n > 500. When investigations of such scale were not available for a nation, we included studies that reported the seroprevalence in provinces 26,45 , counties 37 , regions 42 , governates 39 , major cities and towns 20,29,32,36,40 , districts 54 , or municipalities 27,30,35 , with populations that were representative of the general population of the nation.…”

Does misclassification of former tobacco smokers explain the ‘smoker’s paradox’ in the risk of COVID-19? Insights from the Stockholm Public Health Cohort

“…For the reasons above, analyses including ‘former’ in the same reference group as ‘never’ smokers when estimating the relative risk of COVID-19 among ‘current smokers’ may yield downwards biased estimates of associations, reported in previous studies based on such a comparison [15–17].…”