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. 2021 May 21:5:100119.
doi: 10.1016/j.lanepe.2021.100119. eCollection 2021 Jun.

Mass SARS-CoV-2 serological screening, a population-based study in the Principality of Andorra

Cristina Royo-Cebrecos  1   2 , David Vilanova  3 , Joel López  3 , Vanesa Arroyo  4 , Marc Pons  4   5 , Guillem Francisco  4 , Mireia G Carrasco  6 , Josep M Piqué  2 , Sergi Sanz  7   8   9 , Carlota Dobaño  7 , Alberto L García-Basteiro  7   10
Affiliations

Mass SARS-CoV-2 serological screening, a population-based study in the Principality of Andorra

Cristina Royo-Cebrecos et al. Lancet Reg Health Eur. .

Abstract

Background: Andorra is a small country located in the Pyrenees attracting millions of visitors for tourism, mostly associated with skiing, and nature-related activities. As its neighbouring countries, Spain and France, it has been heavily affected by the COVID-19 pandemic. We estimated SARS-CoV-2 seroprevalence in the entire country by universal serological testing under a lockdown environment.

Methods: A total of 77,543 inhabitants of Andorra were invited to participate in the study. From 4-28 May, 2020, two cross sectional serological surveys were conducted using a rapid serological test (nCOV IgG/IgM) on a finger prick blood sample in 59 drive-through or walk-through checkpoints, all over Andorra. We calculated seroprevalence of antibodies against SARS-CoV-2 and analysed the main sociodemographic factors associated with being seropositive.

Findings: 70,494 inhabitants (90.9% of the population) participated in at least one survey. Overall seroprevalence was 11.0%. The most affected age groups were those over 90 years old (15.2%) and 80-89 (13.8%), followed by adults 50-59 (13.6%) and adolescents 10-19 (13.7%). Most seropositive participants, 6,061 (95.1%), were asymptomatic before the surveys. The multivariable analysis showed that the odds of being seropositive was higher among seasonal workers (OR 2.41; 95% CI 1.07-5.45) or in the population living in La Massana region, a popular ski-related area (OR 2.66; 95% CI 2.44-2.89). A higher seroprevalence was observed in those familiar nuclei with greater numbers of cohabitants: 18% in families with 6 household members or more; 13% in medium size families (3/4/5 people) and 12% in small size (1 to 2 people) nuclei.

Interpretation: The prevalence of antibodies against SARS-CoV-2 in the population of Andorra was high during the first wave of the pandemic. Seasonal workers and inhabitants based in La Massana presented a higher seroprevalence. Mass antibody screening allows to identify infection hotspots and should contribute to the design of tailored interventions to prevent SARS-CoV-2 transmission in Andorra.

Funding: Andorran Ministry of Health, Andorran Health Services.

Keywords: Andorra; COVID-19; Diagnostics; Epidemiology; SARS-CoV-2; Screening.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Study participants flowchart.
Figure 2
Figure 2
Seroprevalence against SARS-CoV-2 in Andorra by parish (May 2020). Panel A: first survey; Panel B: second survey; Panel C: overall.
Figure 3
Figure 3
Seroprevalence against SARS CoV-2 in Andorra by household size (May 2020).
See this image and copyright information in PMC

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