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Effect of portable HEPA filters on COVID-19 period prevalence: an observational quasi-interventional study in German kindergartens
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  • Published on:
    On reducing infection risk via air purification
    • Lotta-Maria Oksanen, MD, researcher Helsinki University Hospital, University of Helsinki
    • Other Contributors:
      • Antti Hellsten, Principal Scientist
      • Mikko Auvinen, Senior Researcher

    We appreciate the authors for their interesting article, but we want to highlight issues regarding the interpretation and reproducibility of the research results. The key problems lie in the documentation of measurements and the reporting of essential aspects of the study.

    First, the article does not provide sufficient detail on how ventilation in the participating daycare centers is implemented – whether it is mechanical, gravity-based, or reliant solely on window ventilation. Fundamental information concerning the baseline ventilation is crucial for evaluating and reproducing the study results. When assessing the effectiveness of air purification against airborne infections, it is necessary to establish 1) what is the baseline ventilation capacity which dictates the reference airborne infection risk level and 2) what is the augmented ventilation capacity after introducing air purifiers which, in turn, dictate the expected reduction in the risk level (Rehva 2020; Auvinen et al. 2022; Buonanno et al. 2022). Without knowing the baseline ventilation rates and how they differ between intervention and control groups, it is impossible to assess whether the introduced air purification improves the overall ventilation performance sufficiently to bring the risk level low enough to justify expectations for an observable improvement. After all, it is possible that even after introducing air purifiers the infection risk levels remain high nonetheless (Rehva 2023).


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    Conflict of Interest:
    None declared.
  • Published on:

    Eine interessante Studie mit einem klaren Ergebnis

    Zur Schlußfolgerung: "Es ist bekannt, dass die Ansteckung hauptsächlich über den direkten Luftaustausch von Angesicht zu Angesicht während des Spiels erfolgt und dass die kontaminierte Luft nicht unbedingt vor dem Luftaustausch zwischen Kindern durch den Filter strömt. Die Verwendung von HEPA-Filtern kann auch zu einem Sicherheitsgefühl führen, was zu einem verringerten vorbeugenden Verhalten führt."

    Die Studie enthält keine Untersuchung über den Verhaltensvergleich in den Kindergärten der zwei Kohorten (Mit/Ohne Filter).

    Insofern vermisse ich in der Schlußfolgerung diese Aussage als eine Vermutung kenntlich zu machen.
    Ich finde, daß "Ergebnis" und "Schlußfolgerung" zwei verschiedene Themen sind. Die Schlußfolgerung müßte meines Erachtens lauten: HEPA Filter bringen keinen Vorteil.

    Ich finde die Schlußfolgerung eher in Brosa formuliert und somit abweichend vom vorhergehenden Text der Studie. Für mich macht dies die Qualität der Studie zunichte wenn Vermutungen angestellt werden welche nicht Umfang der Studie waren. Mithin viele Studien nur nach Abstrakt, Ergebnis & Schlußfolgerung lesen.
    Wenn die Studienverfasser einen Beweis nahelegen, dann muß das Verhalten der Kinder in den Kohorten überprüft und nachgewiesen werden.

    Conflict of Interest:
    None declared.