Wearing an upgraded facemask from the standard “surgical” design cuts hospital Covid infections by 100 per cent, a study has found.

Staff working on Covid wards at Addenbrooke’s Hospital in Cambridge who were issued with filtering face piece 3 (FFP3) respirators had a lower infection rate than people in the wider community.

Designed to prevent the transmission of aerosols – tiny disease-carrying particles that can float in the air – the masks are currently only issued to a minority of NHS staff performing tasks deemed to pose the highest risk of infection.

By contrast, the standard issue surgical masks, although fluid-resistant, are looser-fitting, allowing airflow from its sides.

As the second wave started to hit last December, managers at Addenbrooke’s made a unilateral decision to upgrade to the FFP3 mask on all Covid wards.

In a study by the University of Cambridge, they found that the masks provided up to 100 per cent protection.

Hospital-acquired infection has posed a huge problem since the start of the pandemic.

Last month, an analysis of NHS data indicated that up to 8,700 patients have died after catching Covid-19 after being admitted to hospital.

Dr Chris Illingworth, from the MRC Biostatistics Unit at the University of Cambridge, said: “Before the face masks were upgraded, the majority of infections among healthcare workers on the Covid-19 wards were likely due to direct exposure to patients with Covid-19.

“Once FFP3 respirators were introduced, the number of cases attributed to exposure on Covid-19 wards dropped dramatically – in fact, our model suggests that FFP3 respirators may have cut ward-based infection to zero.”

According to the researchers’ mathematical model, the risk of direct infection from working on a non-Covid-19 ward was low throughout the study period, and consistently lower than the risk of community-based exposure.

Both the doctors’ and nurses’ unions have called for higher quality masks for staff.

Rose Gallagher, RCN professional lead for infection prevention and control said: “This important study adds even further weight to the RCN’s continuing call for nursing staff to be better protected from Covid-19 and given routine access to the highest levels of respiratory protective equipment whenever they need it.”

A Department of Health and Social Care spokesperson said: “The safety of the NHS and social care staff has always been our top priority and we continue to work round the clock to deliver PPE to protect those on the frontline.

“Guidance on the appropriate levels and standards of PPE is written by experts and agreed by all four UK chief medical officers.

“Updated infection prevention control guidance was published this month to reflect the latest scientific understanding on how to prevent transmission of Covid-19.

“Emerging evidence and data are continually monitored and reviewed and guidance will be amended accordingly if appropriate.”