ImportanceThe effectiveness of in-room air purification for the reduction of acute respiratory infections (ARIs) in residential aged-care facilities (RACFs) is unknown.ObjectiveTo investigate the effectiveness of in-room air purifiers with high-efficiency particulate air (HEPA)–14 filters in reducing the incidence of ARIs among residents of RACFs.Design, Setting, and ParticipantsThis randomized clinical trial used a multicenter, double-blind, 2-period, 2-treatment crossover design for 6 months from April 7 to October 26, 2023, in 3 RACFs with a bed capacity of 50 to 100 in New South Wales, Australia. The purposive sampling approach included permanent residents in private rooms in the enrolled RACFs. Data collection was performed every 2 weeks and required no additional follow-up beyond the final data collection on October 31, 2023.InterventionAn air purifier containing a HEPA-14 filter was placed in rooms of participants in the intervention group, and an air purifier without a HEPA-14 filter was placed in rooms of the control participants. The groups crossed over after 3 months.Main Outcomes and MeasuresThe primary outcome was the incidence of ARIs, assessed with logistic mixed-model regression.ResultsAmong 135 participants randomized (70 to the intervention-first group and 65 to the control-first group), 78 (57.8%) were female; mean (SD) age was 85.2 (8.6) years. In the intention-to-treat analysis, the use of air purifiers with HEPA-14 filters did not reduce ARIs compared with the control (OR, 0.57; 95% CI, 0.32-1.04; P = .07). Among the 104 participants who completed the entire study, the intervention reduced ARI incidence from 35.6% (37 participants) in the control group to 24.0% (25 participants) in the intervention group (OR, 0.53; 95% CI, 0.28-1.00; P = .048).Conclusions and RelevanceIn this clinical trial investigating use of air purifiers with HEPA-14 filters for reducing ARIs, no significant between-group difference was found in the intention-to-treat analysis. However, a significant reduction in ARIs was identified among participants who completed the entire study. These findings may help inform future large-scale studies of respiratory infectious diseases.Trial RegistrationANZCTR identification: ACTRN12623000347662
