Government pilot set to trial hospital air purifiers in plan to limit Covid outbreaks

Exclusive: Once funding is confirmed, Addenbrooke’s Hospital in Cambridge will install filtration units and air sampling equipment across two of its wards to assess spread of the virus between patients

Samuel Lovett
Science Correspondent
Sunday 12 December 2021 14:10 GMT

Government officials are set to approve a pilot study that will investigate the use of air purifiers and ultraviolet light in hospital wards as part of efforts to tackle outbreaks of Covid-19 within health settings.

Once funding is secured, Addenbrooke’s Hospital in Cambridge will instal filters that combine high-efficiency particulate air (Hepa) and UV technology in two of its wards, where data on the spread of the virus between patients will be collected and then assessed.

The study is similar to the Bradford schools pilot, which is testing separate Hepa and UV purifiers in classrooms, but that study is not as large in scale due to the higher rate of infections within hospitals.

Tens of thousands of patients caught Covid-19 during the first and second waves while receiving treatment in hospital for another health issue, research shows.

Hospital-acquired infections (HAIs) have continued to persist throughout the pandemic, though the spread of the virus in wards has reduced thanks to improved testing and prevention control measures.

However, with the emergence of the omicron variant, which is able to infect the double-vaccinated, health bosses are concerned that Covid cases among staff and patients may start to rise again in hospitals over the coming weeks.

The team behind Addenbrooke’s study has been in lengthy discussions with the UK Health Security Agency (UKHSA) to secure government funding. One source said: “It’s almost approved. We’re nearly there.”

Unlike the Bradford schools pilot, the hospital study will use single filtration units that combine Hepa and UV technologies to clean the air of different infections, including Covid.

A number of these devices have already been rolled out in Addenbrooke’s and begun collecting data – though this has yet to be assessed as part of the research.

The funding from UKHSA will help to pay for around 12 filtration units that will be installed across the corridors and bed bays of two wards, alongside air sampling equipment. The project will cost around £80,000.

A separate study has already been conducted by the same team at Addenbrooke’s, but was focused on two four-bed bays and therefore analysed a smaller volume of air.

The new research intends to provide a bigger and clearer picture on the extent that purifiers clear the air and limit the spread of Covid infection between patients within hospital settings. It will also seek to provide data on the transmission of the virus from healthcare workers to patients.

“We know that this technology removes virus, bacteria, fungi from the air but what we don’t know is how much of an impact that has on patient infections,” said one source with knowledge of the study.

“We know that about 90 per cent of patient infections come from other patients. If the majority of that is beyond two metres, then ventilation would be expected to mitigate the majority of it, because that’s the bit that it’s cleaning.

“If infection, however, is happening when patients get close to each other – so, say, one person goes up and talks to another person at their bedside – there’s very little ventilation can do because the concentration is so great.”

The source said their early estimates suggested that the use of filtration units in hospitals could reduce Covid infections by 20 to 50 per cent.

Purifiers remove small particles from the air such as dust, allergens and contaminants, and work by filtration or UV light.

Hepa purifiers have a fan to draw polluted air into the device, which then passes through a filter, usually made of fibreglass, paper or mesh, to catch the tiny particles. The purified air is then pumped back into the room.

UV purifiers use short-wave ultraviolet light which can inactivate viruses, bacteria and other pathogens by breaking the chemical bonds of their DNA or RNA.

The source explained that the study would work by “looking backwards at how many infections” the two wards had before the filters were installed, and then “look forward to how many infections we get once the units are in place”.

It’s hoped the project will be up and running by the end of January, once the green light is given by UKHSA. Under current proposals, the research would run for a year.

The source said the research may lead to national rollout if it points to a clear reduction in Covid infections. “However, if we don’t get clinically significant results – we might only see a [faint] trend – then it could go on to simply inform a larger study”.

It could be the case that purifiers aren’t needed in all health settings, just those with poor air ventilation, the source added.

“It might be the case that older draughty hospitals have better ventilation than newer, more energy-efficient ones and may not benefit as much from air purifiers. You really need to check the air quality first to tell.

“Newer hospitals, which are very good on energy and sealed tight, but poor on ventilation, they haven’t been designed to stop the spread of an airborne pathogen. These hospitals might need to be the future focus in improving air quality and reducing transmission.”

It’s expected the research will produce “higher quality data” than the Bradford schools pilot “because we have the frequent in-patient testing and genetics,” the source added.

As first reported by The Independent, internal NHS data shows that more than 35,000 patients were likely to have been infected with coronavirus while already in hospital between 1 August 2020 and 31 January 2021.

An average of 19.6 per cent of patients with Covid-19 in UK hospitals were meanwhile infected after admission in the middle of May 2020, separate research shows.

In September, scientists said the variation in HAI rates between different hospitals “requires urgent investigation” to ensure the most effective measures can be put in place to reduce infection.

The UKHSA said further details around the Addenbrooke’s Hospital project will be announced in due course.

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