Even minor respiratory infections can become life-threatening in vulnerable older residents in care homes, and staff can also become unwell. Current infection control methods mainly rely on keeping surfaces clean, washing hands and wearing face coverings to reduce the spread of germs.
High efficiency particulate air (HEPA) filters are known to improve air quality and clean the air of microbes in laboratory settings, but this is the largest ‘real-world’ study to date to test if they reduce infections in care homes.
The National Institute for Health and Care Research (NIHR)-funded AFRI-c (Air Filters to Prevent Respiratory Infections including Covid-19 in Care Homes) study is also the first to look at whether portable HEPA filters can reduce common respiratory and other infections in care homes in England.
Comparing care homes with and without the HEPA filters, the study found that the air filters did not make any difference to the number of respiratory infections in residents or the number of gastrointestinal, urinary or skin infections.
There was also no difference in:
- the number of antibiotic prescriptions or hospitalisations
- residents’ physical health, including the number of falls and near falls
- the number of staff-reported sickness days between the two groups.
There were high levels of compliance, with care home managers and residents following the manufacturer’s instructions for air filter set up, location and use. No harms were reported.
The study’s findings are consistent with two systematic reviews which concluded that portable HEPA filters do not reduce respiratory infection rates in private homes and offices.
Study design
Ninety-one care homes and 1,158 older people took part in the trial across England between 2021 and 2024. Each care home was allocated randomly to either receive HEPA filters or not, for one winter. Forty-seven care homes were given up to five filters to use in communal areas and one filter per bedroom for up to 16 residents. Care home staff were asked to keep the filters switched on continuously (day and night) from September until May.
The remaining 44 care homes did not use any air filters during that period. All 91 care homes were asked to continue with their usual methods of infection control and cleaning.
Care home staff collected information each day on whether residents had symptoms of infections (like sneezing, coughing and wheezing). They also recorded how many days staff were off work due to sickness. Data was also collected from residents’ GP medical records, with their permission, about diagnosed infections, antibiotic prescriptions and hospitalisations.
Care home managers, residents and the HEPA filter manufacturer were consulted to ensure air filter effectiveness was balanced with acceptability (avoiding draughts and noise disturbance for residents) and power consumption.
Alastair Hay, a GP and Professor of Primary Care in the Centre for Academic Primary Care Infection Group at the University of Bristol, who led the study, said: “Our study has clearly shown that HEPA filters do not prevent respiratory infections, like coughs, colds, flu or COVID-19, when used in older people’s care homes. It is important, therefore, that care homes continue with standard infection control methods, including vaccinations, regular cleaning and hand washing.
“HEPA filters are not currently widely used in care homes in the UK. Potential cost-savings if care homes in England do not purchase HEPA filters are estimated to be £30 million per year.”
Ruth Kipping, Professor of Public Health at Bristol Medical School: Population Health Sciences, and co-author, added: “This is the first robust trial of HEPA filter use in care homes. In the light of our findings, we recommend that care home managers, residents and local authorities do not invest in portable HEPA filters for the purpose of reducing infections in care homes.
“Further research is needed in other health care settings and with other age groups before we can be sure that portable HEPA filters are universally ineffective for infection control. More research will become necessary if manufacturers develop air filters that can operate at higher flow rates that are acceptable to staff and residents.”
Professor Adam Briggs, Director of NIHR’s Public Health Research Programme, said: “This study shows that portable HEPA air filters do not prevent infections in care homes any better than routine measures such as washing hands and keeping surfaces clean.
“This can potentially save care homes millions of pounds and is a great example of how real-world NIHR-funded research can support the sector to make effective and efficient use of limited resources.”
Main study limitation
The main study limitation identified by the authors is that it is not possible to be sure whether the HEPA filters cleaned the air of infectious germs but infections continued to result from transmission by other means (such as through touching contaminated surfaces), or whether the air filters did not clean the air resulting in airborne transmission of infections. This would have required care homes to measure air quality, taking extra time and costing more.
“While this would have been useful to know for the design of futures studies”, said Professor Hay, “this does not change the main finding of no difference in infection rates between care homes that used the HEPA filters and those that did not.”
Papers
‘High efficiency particular air filters to prevent symptomatic winter respiratory infections including COVID-19 in care homes: the AFRI-c pragmatic cluster randomised trial’ by Alastair Hay et al. in JAMA Internal Medicine
‘Implementation and acceptability of high efficiency particulate air filters to reduce respiratory infections in care homes: process evaluation of the AFRI-c cluster randomised controlled trial’ by Sophie Rees et al. in PLOS One