Seroprevalence of severe acute respiratory syndrome coronavirus 2 in Slovenia : results of two rounds of a nationwide population study on a probability-based sample, challenges and lessons learned

Poljak, Mario (author), Oštrbenk Valenčak, Anja (author), Štrumbelj, Erik (author), Maver Vodičar, Polona (author), Vehovar, Vasja (author), Resman Rus, Katarina (author), Korva, Miša (author), Knap, Nataša (author), Seme, Katja (author), Petrovec, Miroslav (author), Zupan, Blaž (author), Demšar, Janez (author), Kurdija, Slavko (author), Avšič-Županc, Tatjana (author)

Objectives: Seroprevalence surveys provide crucial information on cumulative severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure. This Slovenian nationwide population study is the first longitudinal 6-month serosurvey using probability-based samples across all age categories. Methods: Each participant supplied two blood samples: 1316 samples in April 2020 (first round) and 1211 in October/November 2020 (second round). The first-round sera were tested using Euroimmun Anti-SARS-CoV-2 ELISA IgG (ELISA) and, because of uncertain estimates, were retested using Elecsys Anti-SARS-CoV-2 (Elecsys-N) and Elecsys Anti-SARS-CoV-2 S (Elecsys-S). The second-round sera were concomitantly tested using Elecsys-N/Elecsys-S. Results: The populations of both rounds matched the overall population (n = 3000), with minor settlement type and age differences. The first-round seroprevalence corrected for the ELISA manufacturer's specificity was 2.78% (95% highest density interval [HDI] 1.81%–3.80%), corrected using pooled ELISA specificity calculated from published data 0.93% (95% CI 0.00%–2.65%), and based on Elecsys-N/Elecsys-S results 0.87% (95% HDI 0.40%–1.38%). The second-round unadjusted lower limit of seroprevalence on 11 November 2020 was 4.06% (95% HDI 2.97%–5.16%) and on 3 October 2020, unadjusted upper limit was 4.29% (95% HDI 3.18%–5.47%). Conclusions: SARS-CoV-2 seroprevalence in Slovenia increased four-fold from late April to October/ November 2020, mainly due to a devastating second wave. Significant logistic/methodological challenges accompanied both rounds. The main lessons learned were a need for caution when relying on manufacturer-generated assay evaluation data, the importance of multiple manufacturer-independent assay performance assessments, the need for concomitant use of highly-specific serological assays targeting different SARS-CoV-2 proteins in serosurveys conducted in low-prevalence settings or during epidemic exponential growth and the usefulness of a Bayesian approach for overcoming complex methodological challenges.

• Language: English
• Keywords: coronavirus disease 2019, probability-based sample, severe acute respiratory syndrome, seroprevalence, severe acute respiratory syndrome coronavirus 2
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: MF - Faculty of Medicine; FRI - Faculty of Computer and Information Science ; FDV - Faculty of Social Sciences
• Publication status: Published
• Publication version: Version of Record
• Year: 2021
• Number of pages: Str. 1039.e1-1039.e7
• Numbering: Vol. 27, iss. 7
• PID: 20.500.12556/RUL-138699
• UDC: 616.9
• ISSN on article: 1198-743X
• DOI: 10.1016/j.cmi.2021.03.009
• COBISS.SI-ID: 62248195
• Publication date in RUL: 10.08.2022

Record is a part of a journal

• Title: Clinical microbiology and infection
• Publisher: Elsevier, European Society of Clinical Microbiology and Infectious Diseases
• ISSN: 1198-743X
• COBISS.SI-ID: 71154

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: koronavirusna bolezen 2019, vzorec na podlagi verjetnosti, hud akutni respiratorni sindrom