Seroprevalence of SARS-CoV-2 IgG Antibodies in Utsunomiya City, Greater Tokyo, after first pandemic in 2020 (U-CORONA): a household- and population-based study

  1. Nobutoshi Nawa
  2. Jin Kuramochi
  3. Shiro Sonoda
  4. Yui Yamaoka
  5. Yoko Nukui
  6. Yasunari Miyazaki
  7. Takeo Fujiwara

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Abstract

Background

The number of confirmed cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in Japan are substantially lower in comparison to the US and UK, potentially due to the under-implementation of polymerase chain reaction (PCR) tests. Studies reported that more than half of the SARS-CoV-2 infections are asymptomatic, confirming the importance for conducting seroepidemiological studies. Although the seroepidemiological studies in Japan observed a reported prevalence of 0.10% in Tokyo, 0.17% in Osaka, and 0.03% in Miyagi, sampling bias was not considered. The study objective was to assess the seroprevalence of SARS-CoV-2 in a random sample of households in Utsunomiya City in Tochigi Prefecture, Greater Tokyo, Japan.

Methods

We launched the Utsunomiya COVID-19 seROprevalence Neighborhood Association (U-CORONA) Study to assess the seroprevalence of COVID-19 in Utsunomiya City. The survey was conducted between 14 June 2020 and 5 July 2020, in between the first and second wave of the pandemic. Invitations enclosed with a questionnaire were sent to 2,290 people in 1,000 households randomly selected from Utsunomiya basic resident registry. Written informed consent was obtained from all participants. The level of IgG antibodies to SARS-CoV-2 was assessed by chemiluminescence immunoassay analysis.

Results

Among 2,290 candidates, 753 returned the questionnaire and 742 received IgG tests (32.4 % participation rate). Of the 742 participants, 86.8% were 18 years or older, 52.6% were women, 71.1% were residing within 10 km from the test clinic, and 89.2% were living with another person. The age and sex distribution, distance to clinic and police district were similar with those of non-participants, while the proportion of single-person households was higher among non-participants than participants (16.2% vs. 10.8%).

We confirmed three positive cases through quantitative antibody testing. No positive cases were found among the people who live in the same household as someone with positive. All cases were afebrile. The estimated unweighted and weighted prevalence of SARS-CoV-2 infection were 0.40% (95% confidence interval: 0.08-1.18%) and 1.23% (95% confidence interval: 0.17-2.28%), respectively.

Conclusion

This study suggests the importance of detecting all cases using PCR or antigen testing, not only at a hospital, but also in areas where people assemble. Further prospective studies using this cohort are needed to monitor SARS-CoV-2 antibody levels.

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  1. ScreenIT

    SciScore for 10.1101/2020.07.20.20155945: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board StatementConsent: Written informed consent was obtained from all participants.
    IRB: This study was approved by the research ethics committee at Tokyo Medical and Dental University.
    RandomizationInvitations enclosed with a questionnaire were sent to 2,290 people in 1,000 households randomly selected from Utsunomiya City’s basic resident registry.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    All analyses were conducted using STATA 14 (StataCorp LP, College Station, TX, USA) and R version 3.6.0 (R Core Team, 2019).
    STATA
    suggested: (Stata, RRID:SCR_012763)
    StataCorp
    suggested: (Stata, RRID:SCR_012763)

    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:
    The study limitation is the low participation rate. Also, the study period was relatively long for seroprevalence study. Nonetheless, because we employed a household-based design, participants who do not usually participate in clinical studies may have been pressured to do so by other household members. This study suggests the importance of detecting all cases using PCR or antigen testing, not only at a hospital, but also in areas where people assemble. Further prospective studies using this cohort are needed to monitor SARS-CoV-2 antibody levels.

    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. ScreenIT

    SciScore for 10.1101/2020.07.20.20155945: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board StatementWritten informed consent was obtained from all participants.RandomizationInvitations enclosed with a questionnaire were sent to 2,290 people in 1,000 households randomly selected from Utsunomiya basic resident registry.Blindingnot detected.Power Analysisnot detected.Sex as a biological variableOf the 742 participants, 86.8% were 18 years or older, 52.6% were women, 71.1% were residing within 10 km from the test clinic, and 89.2% were living with another person.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    All analyses were conducted using STATA 14
    STATA
    suggested: (Stata, SCR_012763)
    (StataCorp LP, College Station, TX, USA) and R version 3.6.0 (R Core Team, 2019).
    StataCorp
    suggested: (Stata, SCR_012763)

    Data from additional tools added to each annotation on a weekly basis.

    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 is not a substitute for expert review. SciScore checks for the presence and correctness of RRIDs (research resource identifiers) in the manuscript, and detects sentences that appear to be missing RRIDs. SciScore also checks to make sure that rigor criteria are addressed by authors. It does this by detecting sentences that discuss criteria such as blinding or power analysis. SciScore does not guarantee that the rigor criteria that it detects are appropriate for the particular study. Instead it assists authors, editors, and reviewers by drawing attention to sections of the manuscript that contain or should contain various rigor criteria and key resources. For details on the results shown here, including references cited, please follow this link.

  3. Version published to 10.1101/2020.07.20.20155945 on medRxiv