HEPA Filters in Care Homes: No Reduction in Winter Respiratory Infections According to AFRI-c Trial

Highlight

• The AFRI-c cluster randomized trial tested the effectiveness of portable HEPA filters in communal and bedroom areas of care homes during winter.
• No statistically significant difference in respiratory infection rates or staff absenteeism was found between intervention and control homes.
• Findings suggest that HEPA filtration may not reduce transmission rates significantly in care home settings beyond existing infection prevention measures.
• Care homes should continue standard recommended infection control strategies to mitigate respiratory illnesses among vulnerable residents.

Study Background

Respiratory infections represent a significant health burden for older adults residing in care homes, often leading to increased morbidity, hospital admissions, and mortality during winter months. These infections can spread rapidly due to communal living environments and close contact among residents and staff. Portable high-efficiency particulate air (HEPA) filters have demonstrated efficacy in removing airborne microbes and have been proposed as an adjunct to standard infection prevention and control (IPC) measures. However, clinical evidence supporting the use of HEPA filters to lower respiratory infection incidence in care homes remains limited. The AFRI-c trial was designed to address this gap and generate robust data on whether adding HEPA filtration improves resident health outcomes during winter seasons.

Study Design

The AFRI-c trial was a 2-arm cluster randomized clinical trial conducted in England from September 2021 to May 2024. The study enrolled 91 care homes accommodating 20 or more residents in individual bedrooms, with or without nursing and dementia care provisions. Care homes were randomized to receive either:

• Intervention: Up to 5 portable HEPA filters with a clean air delivery rate of 160 m³/h placed in communal rooms, plus up to 16 filters with 60 m³/h delivery rate in bedrooms.
• Control: No HEPA filters deployed.

Both groups continued usual infection prevention and control measures, such as vaccination programs, hand hygiene, and environmental cleaning.

The primary outcome was the rate of respiratory infection episodes per winter per bedroom resident, accounting for exposure to both bedroom and communal room filters. Secondary outcomes included staff absenteeism rates. The trial also analyzed outcomes for residents exposed only to communal filters to delineate any localized effects.

Key Findings

The study randomized 91 care homes: 47 homes (569 bedroom residents; median age 87 years; 70.0% female) to the intervention arm and 44 homes (589 residents; median age 88 years; 71.8% female) to the control. Major findings include:

• Primary Outcome (Respiratory Infection Rates): The number of infections per winter per bedroom resident was 0.99 in the intervention group versus 1.04 in controls. The adjusted incident rate ratio was 0.92 (95% CI, 0.64-1.33; P=0.67), indicating no statistically significant difference.
• Secondary Outcome (Staff Absenteeism): Staff absenteeism rates were lower in the intervention group (adjusted incident rate ratio 0.80; 95% CI, 0.55-1.16; P=0.24), but this difference was not statistically significant.
• Exposure to Communal Room HEPA Filters Only: Similar lack of significant benefit was observed for residents exposed only to filters in communal areas.

No safety concerns related to HEPA filter use were reported.

Expert Commentary

The AFRI-c trial provides high-quality evidence from a large pragmatic study that portable HEPA filters, when added to established infection control practices, do not significantly reduce respiratory infection rates or staff absenteeism in care home settings during winter. This aligns with the complex, multifactorial transmission dynamics of respiratory pathogens, where airborne particles represent only one route among others such as close contact and fomite transmission.

Limitations include that the study was conducted during a time when extensive IPC measures, including COVID-19-related interventions, were already in place, potentially reducing the marginal benefit of additional air filtration. Also, the clean air delivery rates used were moderate, and the effectiveness of higher capacity filtration or integrated ventilation systems was not studied. Generalizability is constrained to care homes with similar staffing, physical layouts, and IPC policies.

Biologically, while HEPA filters efficiently remove small particles—including many respiratory pathogens—their impact on clinical infection rates depends on factors such as time spent in filtered zones, adherence to other precautions, and pathogen-specific transmission characteristics.

Conclusion

The AFRI-c cluster randomized trial demonstrated that deploying portable HEPA filters in communal and bedroom areas of care homes did not yield a statistically significant reduction in winter respiratory infection episodes or staff absenteeism compared to standard infection control measures alone. Care homes should maintain and optimize recommended prevention strategies, including vaccination, hand hygiene, environmental cleaning, and outbreak management protocols. Future research might explore combining air filtration with engineering controls or targeting specific pathogens or outbreak scenarios.

Funding and Clinical Trial Registration

The trial was registered under ISRCTN number ISRCTN63437172. Funding sources were not detailed in the abstract but can be found in the full publication in JAMA Internal Medicine.

References

1. Hay AD, Brierley RCM, Turner N, et al. High-Efficiency Particulate Air Filters to Prevent Winter Respiratory Infections in Care Homes: The AFRI-c Cluster Randomized Clinical Trial. JAMA Intern Med. 2026 Jul 27. doi:10.1001/jamainternmed.2026.42507455.

2. Morawska L, Milton DK. It is Time to Address Airborne Transmission of COVID-19. Clin Infect Dis. 2020 Sep 1;71(9):2311-2313.

3. Centers for Disease Control and Prevention (CDC). Infection Control Guidance for Long-Term Care Facilities. Updated 2024.

4. Li Y, Qian H, Hang J, et al. Evidence for probable aerosol transmission of SARS-CoV-2 in a poorly ventilated restaurant. Build Environ. 2021 Jan 15;196:107788.