Rapid increase of SARS-CoV-2 seroprevalence during the 2020 pandemic year in the population of the city of Tirana, Albania

  1. Genc Sulcebe
  2. Alban Ylli
  3. Fabian Cenko
  4. Margarita Kurti-Prifti

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Abstract

Introduction

While the identification of anti SARS-CoV-2 antibodies has been used to measure the hidden circulation of the COVID-19 in communities, there are few publications on the dynamics of SARS-CoV-2 seroprevalence during both waves of 2020. This study provides original data about the change in proportion of individuals showing immune response to COVID-19 between beginning of July and end of December 2020.

Methods

The study was conducted in two rounds, 27 June −3 July, and 21-28 December 2020, using two independently selected samples of individuals 20-70 years old. Study participants were randomly selected from lists of the inhabitants of the catchment communities of four primary health care centers in Tirana City. Serological testing was performed by an ELISA method which determines IgG class antibodies anti S1 protein of SARS-CoV-2 virus. The validity of the method was tested in a sample of blood donor’s sera of 2018.

Results

The proportion of individuals classified as seropositive during the first round, in early July was 7.5% (95% CI: 4.3% −10.7%). The proportion rose sharply in the second round, by late December 2020, reaching 48.2% (95% CI: 44.8% −51.7%). The same increasing pattern was observed in all studied categories. No statistical significance was found between men and women and between age categories. The prevalence of seropositive individuals was always significantly higher among those who reported symptoms and those who had done the molecular test.

Conclusion

The ratio of total infected cases over confirmed cases was estimated to be higher than 10 to 1 in Albania. The rapid increase in SARS-CoV-2 seroprevalence observed in Tirana City may have been facilitated by a number of factors, including the very low infection exposure during the period March -May 2020, and the consecutive high susceptibility in population. Despite the observed high seroprevalence, one month after the study, COVID-19 incidence continued to increase in Tirana.

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  1. ScreenIT

    SciScore for 10.1101/2021.02.18.21251776: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    Randomizationcenters (HCs) that cover the city of Tirana, four HCs were randomly selected; respectively HC number 3, HC 7
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Serological testing of IgG class anti-S1-CoV-2 antibodies: Serological testing of all blood samples was performed by an ELISA method using a commercially available diagnostic kit which determines IgG class antibodies anti S1 protein of SARS-CoV-2 virus (IgG anti S1-SARS-CoV-2 ELISA, Euroimmun, Luebeck, Germany).
    anti-S1-CoV-2
    suggested: None
    anti S1 protein of SARS-CoV-2 virus (IgG anti S1-SARS-CoV-2 ELISA, Euroimmun, Luebeck, Germany).
    suggested: None
    anti
    suggested: None
    Software and Algorithms
    SentencesResources
    All raw data have been statistically analyzed using the SPSS 20 package programs.
    SPSS
    suggested: (SPSS, RRID:SCR_002865)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    We should also note that our study has some limitations. The sample size of the population especially in the first phase was rather limited and the percentage of seropositivity was calculated with a somewhat wide confidence interval (4.3% to 10.7%). Our study was carried out by the determination of anti-Protein S1 SARS-CoV-2 IgG antibodies. As we observed in our comparative sensitivity study, anti-nucleocapsid (N) SARS-CoV-2 IgG antibodies have at least 10% higher sensitivity than anti S1-SARS-CoV-2 IgG for COVID-19 testing, a finding also reported from other sources (8, 12, 37). From this finding we can infer that if we had used the anti-nucleocapsid (N) SARS-CoV-2 IgG testing, the seroprevalence rate in our population sample could be even higher than that which was obtained by IgG anti S1-SARS-CoV-2 IgG testing. The seroprevalence results, especially in the case of proportions fewer than 5% and especially in the first round of the study, should be interpreted with caution and always within the limits of test validity. Also, in our study we have investigated the seroprevalence of SARS-CoV-2 infection only in Tirana city residents aged 20 to 70 years who have access to public health services.. The fact that the sample does not include those who do not use primary health care or do not collaborate with their health workers should also be taken into consideration when applying the results in general population.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  2. Version published to 10.1101/2021.02.18.21251776 on medRxiv