The effect of strict lock down measures on Covid-19 seroprevalence rate and herd immunity

  1. Maher A. Sughayer
  2. Asem Mansour
  3. Abeer Al Nuirat
  4. Lina Souan
  5. Mohammad Ghanem
  6. Mahmoud Siag

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Abstract

Background

Covid-19 seroprevalence rates and serological tests are important tools in understanding the epidemiology of the disease and help in the fight against it. Seroprevalence rates vary according to the population studied and the test employed and they range from 0.133 to 25.7%. The purpose of this study is to assess the seroprevalence rate in a population of healthy blood donors living under strict lockdown measures in Jordan which has in total 144 confirmed cases per million population.

Methods

Left-over sera and plasma samples from 746 healthy blood donors were tested using a commercially available FDA approved kit having a sensitivity and specificity of 100% and 99.8% respectively. External positive controls were used for validation.

Results

More than 80% of the donors were men 18-63 year old and residing in the capital city of Jordan, Amman. All tested specimens were negative yielding a zero seroprevalence rate in this healthy blood donor population.

Conclusion

Strict lockdown measures effectively limit intracommunity spread of the infection, however at the cost of lack of any acquired community immunity. Additionally the use of highly specific test is recommended in low prevalence setting.

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  1. Version published to 10.1101/2020.06.06.20123919v2 on medRxiv
  2. ScreenIT

    SciScore for 10.1101/2020.06.06.20123919: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    RandomizationSubjects and samples: Left over sera and or plasma collected routinely during the process of blood or apheresis platelet donations were randomly chosen for the study.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    The assay uses a recombinant protein representing the nucleocapsid (N) antigen for the determination of antibodies against SARS-CoV-2.
    SARS-CoV-2
    suggested: None

    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:
    This seroprevalence rate of zero is probably real despite the limitation of the relatively small sample size. The most likely explanation therefore is the absence of community exposure secondary to the strict lockdown measures undertaken by the authorities in Jordan. The measures implemented were therefore extremely efficient in preventing the disease spread. On the one hand it really helped the health authorities to have the epidemic under control with no extra constrains or overburden on the health response system with the impressive result of only few hundred cases registered, traced to imported cases form other countries, and of total deaths of less than 10 patients, all of whom were elderly and or with preexisting comorbidities. The number of deaths per million population is extremely low as compared to other countries of the world. On the other hand Jordan may face a real problem should there be a second wave of infection before the development of an effective vaccine or therapy because of the absence of any community or herd immunity. One may hope before that occurs, a natural decrease in virulence similar to what happened with other corona viruses takes place. This situation of having an immune-naive community raises concern for some in regards to the strict lockdown measures and weather they were really justified in view of the very low number of cases registered and the early clear evidence that no community spread had occurred. The price to be paid in terms of lack...

    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.
    • Thank you for including a protocol registration statement.

    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 10.1101/2020.06.06.20123919v1 on medRxiv