Design: Cluster randomised trial
Population: 91 care homes in England; about 1160 bedroom residents
Primary outcome: Respiratory infections per resident per winter
Effect: 0.99 vs 1.04; adjusted IRR 0.92 (95% CI 0.64 to 1.33)

AFRI-c randomised 91 English care homes, each for one winter between 2021 and 2024, to portable HEPA filters in communal areas and bedrooms or to usual infection control. Residents had a median age of 87. It was published in JAMA Internal Medicine in September.

Respiratory infections per winter were 0.99 per bedroom resident with filters and 1.04 without (adjusted rate ratio 0.92, 95% CI 0.64 to 1.33). Staff absenteeism did not differ (0.80, 0.55 to 1.16). Communal-only exposure showed the same pattern.

Filters that clear airborne microbes in the laboratory did not translate into fewer infections here. Care homes and those advising them should put effort into vaccination, isolation and hand hygiene before buying filters.

Prioritise influenza, COVID-19 and RSV vaccination for residents and staff.
Maintain isolation and hand hygiene during outbreaks.
Do not recommend HEPA filters as a standalone infection-control measure for care homes.

Why it matters

It challenges an intuitive, costly intervention that many facilities adopted after the pandemic.

The statistics, in plain English

The rate ratio of 0.92 suggests at most a small effect, and the interval (0.64 to 1.33) is wide enough to include both a useful benefit and a harm. The trial therefore rules out a large benefit but not a modest one.