Air cleaning reduces incident infections in day care - an interventional crossover study

  1. Ville Vartiainen
  2. Inga Ehder-Gahm
  3. Johanna Hela
  4. Anni Luoto
  5. Jussi-Pekka Juvela
  6. Petra Nikuri
  7. Aimo Taipale
  8. Natalia Lastovets
  9. Sampo Saari
  10. Ilpo Kulmala
  11. Arto Säämänen
  12. Enni Sanmark
  13. Piia Sormunen

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Abstract

Background

While possibility of airborne transmission in the spread of common respiratory infections, there is no consensus on the relative importance of airborne infection route in real-life. This study aimed to investigate the significance of the airborne transmissions and the effectiveness of air cleaning in reducing infections among children in daycare.

Methods

A cross-over study was conducted in four daycare centers in Helsinki. All children attending the daycare were invited to participate (n = 262) and the sole inclusion criterion was that the children were expected to stay in the same day care center for the two-year duration of the study. 51 subjects were included in the final analysis. Clean air flow rate was increased by 2.1-2.9 times compared to baseline mechanical ventilation of the premises. The effect of intervention was assessed using negative binomial regression.

Results

The intervention reduced incident infections from 0.95 to 0.78 infections per child per month among the children (primary outcome) in daycare. The reduction attributed to intervention in the statistical model was 18.0 % (95% CI 2.1-31.3 %, p = 0.028).

Conclusions

We observed a significant decrease in incident infections without implementing any other infection mitigation strategies but air cleaning. Our results challenge the current paradigm which emphasizes fomite and contact transmission and infection control measures that target these pathways. As ventilation and air cleaning can only affect particles able to float in the air stream, our results support the significance of airborne transmission among common respiratory pathogens as well as air cleaning as an infection control measure.

Article activity feed

  1. PREreview

    This Zenodo record is a permanently preserved version of a PREreview. You can view the complete PREreview at https://prereview.org/reviews/13871893.

    RR/ID Strength of Evidence Scale rating by reviewer: Potentially informative.

    Review:  This preprint provides evidence for the effect of air cleaning with portable room air cleaners (PAC) in reduction of airborne transmission of common infections in day care units. The authors collected information through weekly electronic surveys answered by parents, and the study demonstrated clinically and statistically significant reduction in incident infections in daycares as the primary outcome, and the secondary outcome of parents' absence from work did not reach statistical significance. The manuscript challenges the current paradigm that emphasizes fomites and contact transmission, and though the findings may provide insight to broader research understandings, the importance of current prevention techniques such as hand washing should not be overlooked, as they continue to prevent transmission of other common non-airborne diseases such as acute gastroenteritis. The manuscript discusses some limitations however, the manuscript had no exclusion criteria, with the sole inclusion criterion that the children were expected to stay in the same daycare center for the two-year duration of the study. The manuscript can benefit from further exploration of exclusion criteria, as some children are only in daycare for half-days and only 2-3 times a week, thus limiting exposure in the day care setting. This may skew findings particularly with a small N value of 51 subjects in the final analysis. Additionally, using questionnaires from parents may not be objective enough as an indicator of illness, as symptoms of allergies and cold symptoms often have similar presentation particularly at the beginning of illness. Furthermore, the manuscript does not clearly present recommendable actions that result from the findings. The study utilized 45 PACs alongside existing ventilation systems, and the issue of practicality and accessibility to most daycares should be considered. Overall, this study is interesting and demonstrates the potential value of exploring better control of common airborne illnesses in day care centers with additional use of air clearing devices.

    Competing interests

    The author declares that they have no competing interests.

  2. Version published to 10.1101/2024.09.25.24314350v1 on medRxiv