Classroom Air Purifiers for Reducing School Absence: Protocol for a Cluster-randomized, Parallel, Two-arm, Group Sequential Superiority Trial
试验速览
- 阶段
- 不适用
- 状态
- Enrolling By Invitation
- 发起方
- 入组人数
- 72
- 试验地点
- 2
- 主要终点
- Student absenteeism
研究概览
简要总结
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.
研究设计
- 研究类型
- Interventional
- 分配方式
- Randomized
- 干预模型
- Sequential
- 主要目的
- Prevention
- 盲法
- Triple (Participant, Investigator, Outcomes Assessor)
盲法说明
School staff, participating teachers, and students will be blinded to treatment allocation via the use of sham air purifiers in the control group. The researchers responsible for installing the air purifiers will also be blinded. To ensure this, all air purifier units will be configured and labeled with serial numbers indicating whether they are sham or functional devices, with one identifier placed in a clearly visible location and another in an inaccessible location. Prior to installing, the visible identifier will be replaced with a label displaying the school and classroom names according to an allocation key, which will be securely stored and accessible only to a single designated researcher (SH). This researcher will configure the air purifiers assigned to the control and intervention arms and will be the sole individual with knowledge of treatment allocation until the point of unblinding
入排标准
- 年龄范围
- 10 Years 至 —（Child, Adult, Older Adult）
- 性别
- All
- 接受健康志愿者
- 是
入选标准
- •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.
排除标准
- 未提供
结局指标
主要结局
Student absenteeism
时间窗: From enrollment to the end of intervention at 12 weeks
The primary outcome is the number of student-days of absence per classroom, measured each week. The investigators will define a student day of absence as a day for which a student is absent for the entire day. The investigators will not distinguish between the specific students who are absent (i.e., two days of absence will be counted for one student who is absent on two days, and for two students absent for one day each).
次要结局
- Self-reported absence due to respiratory infections among teachers(From enrollment to the end of intervention at 12 weeks)
- Adverse events(From enrollment to the end of the intervention at 12 weeks)
- Incidence of self-reported respiratory symptoms consistent with respiratory infections among teachers(From enrollment to the end of the intervention at 12 weeks)
- Teachers reporting respiratory infections(From enrollment to the end of the intervention at 12 weeks)
- Teacher perceptions of air quality in classrooms(From enrollment to the end of the intervention at 12 weeks)