Classroom Air Purifiers for Reducing School Absence

Официальное название

Classroom Air Purifiers for Reducing School Absence: Protocol for a Cluster-randomized, Parallel, Two-arm, Group Sequential Superiority Trial

Обзор

Background Respiratory infections like influenza and SARS-CoV-2 pose significant global health risks due to their high transmissibility and severity. SARS-CoV-2 has caused over 7 million deaths worldwide, and the Lancet Commission estimates a \>20% chance of a similar respiratory virus pandemic within a decade. Schools, often poorly ventilated, are high-risk settings for transmission. While COVID-19 school closures may have reduced transmission, they likely caused learning loss, mental health issues, and increased burdens on parents and caregivers. Air purifiers with HEPA filters may offer a non-disruptive mitigation strategy, but the evidence to support their effectiveness in reducing viral transmission is weak. This protocol describes a cluster-randomised, parallel, two-arm, group sequential superiority trial with an interim analysis-to allow early stopping for efficacy or futility-to estimate the effect of portable air purifiers with HEPA filters in primary school classrooms on student absenteeism. Research Questions The primary question is whether installing and operating air purifiers with HEPA-filters (intervention) reduce student absenteeism (primary outcome) compared to sham air purifiers (control). Secondary questions examine whether the intervention reduces teacher absenteeism due to respiratory infections, rate and 12-week risk of self-reported respiratory infections among teachers, and teachers' perceived air quality compared to sham air purifiers. If the trial estimates a statistically significant effect for the primary outcome, a cost-consequence analysis will evaluate the direct and indirect costs associating with operating air purifiers against the potential benefits of reduced student and teacher absenteeism. A process evaluation will explore mechanisms of effect. Methods and Analysis This group sequential trial will randomize schools (clusters) 1:1 to intervention or control arms in two stages: winter 2025/2026 (N = 32 schools; \~736 students) and winter 2026/2027 (N = 30 schools; \~690 students). Eligible schools must have classrooms suitable for portable air purifiers, \>10 students in grades 5-7 (typically aged 10-13 years), and principal consent. Intervention and control classrooms will each receive two portable air purifiers with HEPA-filters operating at a performance equivalent to 3.0 and 0.3 air changes per hour, respectively, with control purifiers acting as shams. Outcomes will be measured during and at the end of a 12-week period. The primary outcome is student absenteeism, measured as full child-days of absence aggregated at the class level. An interim analysis is planned at the end of the first stage, with error-spending O'Brien-Fleming stopping boundaries that are binding for efficacy and nonbinding for futility. The primary estimand is the marginal incidence rate ratio of student absences, estimated using generalized estimating equations with a negative binomial model to account for overdispersion. Prespecified stopping boundaries will determine stopping, with efficacy boundaries being binding. Treatment effects will be estimated using cluster-bootstrapped confidence intervals adjusted to provide strong control on overall type I and II error probabilities, and a bias correction will be applied if the trial is stopped early for efficacy. All analyses will follow the intention-to-treat principle. Ethics and Dissemination The trial has been approved by the Regional Committees for Medical and Health Research Ethics and the National Research Ethics Committee. Results will be disseminated to stakeholders, participants and the public through peer-reviewed journals, scientific meetings and social media.

Вмешательства

• Устройство Air purifiers
  Air purifiers
• Устройство Sham air purifiers
  Sham air purifiers

Первичные конечные точки

• Student absenteeism [Срок оценки: From enrollment to the end of intervention at 12 weeks]

Вторичные конечные точки (5)

• Self-reported absence due to respiratory infections among teachers [Срок оценки: From enrollment to the end of intervention at 12 weeks]
• Incidence of self-reported respiratory symptoms consistent with respiratory infections among teachers [Срок оценки: From enrollment to the end of the intervention at 12 weeks]
• Teachers reporting respiratory infections [Срок оценки: From enrollment to the end of the intervention at 12 weeks]
• Teacher perceptions of air quality in classrooms [Срок оценки: From enrollment to the end of the intervention at 12 weeks]
• Adverse events [Срок оценки: From enrollment to the end of the intervention at 12 weeks]

Критерии участия

There are two general trial populations. The first population is primary school children in Norway. Primary school children in primary schools meeting the following criteria will be eligible:

• Schools with more than 10 students in either 5th, 6th, or 7th grade (typically aged 10-13 years).
• Schools with at least one classroom of sufficient dimensions to accommodate the installation of two portable air purifiers.
• The school principal accepts the installation of air purifiers in at least one classroom in the 5th, 6th, or 7th grade that meets the first two inclusion criteria.

For logistical and administrative reasons, the investigators will try to limit the sampling frame to schools in municipalities located close our offices in Oslo. These municipalities include several large towns with populations of around 30 000 to 100 000 people, as well as sparsely populated rural areas, and are therefore reasonably representative of Norway and many other countries. The investigators will enlarge the sampling frame as necessary.

The second population is teachers at primary schools in Norway. Teachers meeting the following criteria will be eligible.

• Be the main class teacher of one or more of the classrooms included in the trial.
• Provide informed consent.

Критерии приведены из реестра в оригинале (на английском). Окончательную оценку соответствия проводит исследовательский центр.

Здоровые добровольцы: Да

Дизайн исследования

Распределение

Рандомизированное

Модель

Последовательный дизайн

Маскирование

Тройное слепое

Основная цель

Профилактика

Центры проведения

Норвегия · 1 центр

• Norwegian Institute of Public Health — Oslo

Публикации

• Solberg RB, Holos SB, Elgersma IH, Elstrom P, Rose CJ, Helleve A, Gopinathan U, Fretheim A. Classroom air purifiers for reducing school absence: study protocol for a pragmatic, cluster-randomised, parallel, two-arm, group sequential superiority trial. BMJ Open. 2025 Dec 24;15(12):e109659. doi: 10.1136/bmjopen-2025-109659. PMID 41448709

Идентификаторы

NCT: NCT07119333 · 737650

Первоисточники (государственные реестры)

• ClinicalTrials.gov (NIH, США)

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