HEPA filters in care homes did not reduce infections, trial finds
A Bristol-led trial found portable HEPA filters did not cut infections in English care homes, raising doubts about buying them for infection control.
By Tom Brennan · Health & Medicine Correspondent
4 min read
A University of Bristol-led trial found that portable HEPA filters in care homes did not reduce respiratory infections among older residents. The findings matter because care homes face high risks from coughs, colds, flu and COVID-19, and the study authors said managers should keep relying on established controls such as vaccination, cleaning and hand washing.
The trial, published in JAMA Internal Medicine, compared long-term care facilities in England that used portable high-efficiency particulate air filters with facilities that did not. A related process evaluation was published in PLOS One.
Do HEPA filters reduce infections in care homes?
In this trial, they did not. According to the University of Bristol team, facilities using the filters had no reduction in respiratory infections, and there was also no difference in gastrointestinal, urinary or skin infections.
The researchers also found no difference between the filter and no-filter groups in antibiotic prescribing, hospital admissions, residents’ physical health measures including falls and near falls, or staff-reported sick days. The study reported good adherence to the manufacturer’s instructions for where to place the filters and how to use them, and no harms were reported.
How the trial was run
The AFRI-c trial, short for Air Filters to Prevent Respiratory Infections including COVID-19 in Care Homes, included 91 long-term care facilities and 1,158 older residents in England between 2021 and 2024. The facilities were randomly assigned to use filters or continue without them for one winter.
Forty-seven facilities received up to five filters for communal spaces and one filter for each bedroom for as many as 16 residents. Staff were asked to run the devices continuously, day and night, from September through May. The other 44 facilities did not use air filters during that period.
All participating facilities continued their usual cleaning and infection-control routines. Staff recorded residents’ daily symptoms, such as sneezing, coughing and wheezing, and logged staff sickness absence. With permission, researchers also used residents’ primary care records to gather information on diagnosed infections, antibiotics and hospitalizations.
What are HEPA filters?
HEPA filters are air-cleaning devices designed to capture very small particles from indoor air. The Bristol-led team noted that such filters can improve air quality and remove microbes in laboratory conditions, but said this trial tested whether that translated into fewer infections in real care homes.
The researchers said their findings are in line with two previous systematic reviews that found portable HEPA filters did not reduce respiratory infection rates in homes and offices.
What care homes are being told
Alastair Hay, professor of primary care at the University of Bristol and the study lead, said the results show that portable HEPA filters did not prevent respiratory infections such as coughs, colds, flu or COVID-19 in older people’s long-term care facilities. He said care homes should continue standard measures, including vaccination, regular cleaning and hand washing.
Hay also said HEPA filters are not widely used in UK long-term care facilities, and estimated that avoiding purchases for this purpose could save care homes in England £30 million a year.
Ruth Kipping, a professor of public health at Bristol Medical School and a co-author, said care home managers, residents and local authorities should not buy portable HEPA filters to reduce infections in long-term care facilities, based on the findings. She said more research is needed in other health care settings and age groups, and if manufacturers develop filters that run at higher flow rates acceptable to staff and residents.
Adam Briggs, director of the NIHR Public Health Research Program, said the study suggests portable HEPA filters do not prevent infections in long-term care facilities beyond routine measures such as hand washing and surface cleaning.
The authors identified one main limitation: the trial did not measure whether the filters removed infectious germs from the air. That means the researchers could not tell whether infections continued through other routes, such as contaminated surfaces, or whether the filters failed to reduce airborne transmission. Hay said that uncertainty did not alter the central result: infection rates were the same with or without the filters.
This story draws on original reporting from Medical Xpress.