High secondary attack rate and persistence of SARS-CoV-2 antibodies in household transmission study participants, Finland 2020–2021

  1. Timothée Dub
  2. Anna Solastie
  3. Lotta Hagberg
  4. Oona Liedes
  5. Hanna Nohynek
  6. Anu Haveri
  7. Camilla Virta
  8. Saimi Vara
  9. Mervi Lasander
  10. Nina Ekström
  11. Pamela Österlund
  12. Katja Lind
  13. Hanna Valtonen
  14. Heidi Hemmilä
  15. Niina Ikonen
  16. Timo Lukkarinen
  17. Arto A. Palmu
  18. Merit Melin

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Abstract

Household transmission studies offer the opportunity to assess both secondary attack rate (SAR) and persistence of SARS-CoV-2 antibodies over time.

Methods

In Spring 2020, we invited confirmed COVID-19 cases and their household members to four visits, where we collected nasopharyngeal and serum samples over 28 days after index case onset. We calculated SAR based on the presence of SARS-CoV-2 neutralizing antibodies (NAb) and assessed the persistence of NAb and IgG antibodies (Ab) against SARS-CoV-2 spike glycoprotein and nucleoprotein.

Results

SAR was 45% (39/87), including 35 symptomatic secondary cases. During the initial 28-day follow-up, 62% (80/129) of participants developed NAb. Of those that seroconverted, 90% (63/70), 85% (63/74), and 78% (45/58) still had NAb to early B-lineage SARS-CoV-2 3, 6, and 12 months after the onset of the index case. Anti-spike IgG Ab persisted in 100% (69/69), 97% (72/74), and 93% (55/59) of seroconverted participants after 3, 6, and 12 months, while anti-nucleoprotein IgG Ab levels waned faster, persisting in 99% (68/69), 78% (58/74), and 55% (39/71) of participants, respectively.

Conclusion

Following detection of a COVID-19 case in a household, other members had a high risk of becoming infected. NAb to early B-lineage SARS-CoV-2 persisted for at least a year in most cases.

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  1. Version published to 10.3389/fmed.2022.876532
  2. ScreenIT

    SciScore for 10.1101/2021.07.25.21260925: (What is this?)

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

    Table 1: Rigor

    EthicsField Sample Permit: When collection of a venous samples was not possible, we collected a fingertip sample into a BD Microtainer serum microtube with clot activator (reference number: 365964).
    IACUC: The protocol for the follow-up visits at 6 months was reviewed and approved by the HUS ethical committee and registered under the Development of seroprevalence in Finland during the new coronavirus (SARS-CoV-2) epidemic – serological population study protocol HUS/1137/2020.
    Consent: Informed consent was obtained from all cases and contacts or their parents or legal guardian before any procedure was performed.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    At six months, we used BD Vacutainer 5/3.5 ml gel serum tube with clot activator (reference number: 367957) and a smaller tube 5/2 ml (reference number: 368492) for children.
    BD Vacutainer
    suggested: None
    We performed statistical analysis using STATA 15.1 (StataCorp LP Lakeway, TX, USA).
    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:
    Our study had two main limitations: First, this was not a randomly selected cohort of households as we recruited participants through a voluntary convenience sampling. Second, due to the lag between onset and availability of RT-PCR results, most participants were recruited retrospectively, which prevented us from conducting early household visits to estimate serial intervals for all subjects. Additionally, our estimation of the effective reproductive number was influenced by the limited size of households, with median 3 [IQR:2-4] members. However, this was in line with the demographics of Helsinki, where only 51.5% of households consisted of at least two members including 20.8% of households with 3 or more members.43 Finally, our limited sample size did not allow for comparison of secondary transmission rate depending on age-group of the primary case. Our main strengths were that, unlike most household transmission studies, we measured not only IgG Ab but also NAb to SARS-CoV-2, and that household transmission was assessed over a one month period, providing enough time for the development of antibodies, in case of secondary infection. Finally, only a few participants were lost to follow-up, as 113/129 participated to a convalescent visit at 6 months, allowing us to assess trends in IgG Ab and NAb for 111 study participants out of 129 over a long time period. When living in the same household of an RT-PCR confirmed case, the risk of transmission for other household members is ...

    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.

    Results from scite Reference Check: We found no unreliable references.

    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.

  3. Version published to 10.1101/2021.07.25.21260925 on medRxiv