One in 10 UK patients contracted Covid-19 while receiving treatment in hospitals during the first wave of the coronavirus pandemic, new research suggests.

Residential community care hospitals and mental health hospitals were found to have higher levels of hospital-acquired infections – at 61.9% and 67.5% respectively – compared with hospitals providing acute and general care (9.7%) between March and August 2020.

Researchers have called for possible reasons for variations between setting to be urgently looked at to help implement best practices.

Calum Semple, professor in child health and outbreak medicine at the University of Liverpool and one of the authors of the research published in the Lancet, said: “The reasons for the variation between settings that provide the same type of care requires urgent investigation to identify and promote best infection control practice.

“Research has now been commissioned to find out what was done well and what lessons need to be learned to improve patient safety.”

But Prof Semple added that the rates of hospital-acquired infections are now “at much lower levels”, sitting “somewhere between 2% and 5%”.

He added: “That to me shows that the NHS has learned the lessons.”

The researchers examined records of more than 72,000 patients across 314 hospitals in the UK.

The patients were enrolled in the International Severe Acute Respiratory and emerging Infections Consortium (Isaric) Clinical Characterisation Protocol UK (CCP-UK) study.

They found that at least 11.1% of patients were infected with Covid-19 after being admitted to hospital.

The researchers said: “We estimate between 5,699 and 11,862 patients admitted in the first wave were infected during their stay in hospital.

“This is, unfortunately, likely to be an under-estimate, as we did not include patients who may have been infected but discharged before they could be diagnosed.”

Dr Chris Green, senior clinical lecturer and consultant physician in infectious diseases at the University of Birmingham, and also one of the study authors, said: “There are likely to be a number of reasons why many patients were infected in these care settings.

“These include the large numbers of patients admitted to hospitals with limited facilities for case isolation, limited access to rapid and reliable diagnostic testing in the early stages of the outbreak, the challenges around access to and best use of PPE (personal protective equipment), our understanding of when patients are most infectious in their illness, some misclassification of cases due to presentation with atypical symptoms, and an under-appreciation of the role of airborne transmission.”

He added: “We do have a virus that is very well adapted to humans, and so it will enter the mix of respiratory viruses that circulate particularly in winter months.

“Some of that variation that we have shown in our data needs to be better understood, so that we can try and reduce hospital transmission as much as possible for every site.”