One in 10 patients caught Covid in hospital during first wave, UK study shows

At least one in 10 patients in hospital with Covid-19 during the first wave caught the virus while receiving treatment on a ward for another health issue, new research suggests.

Poor infection prevention measures and limited testing at the beginning of the UK’s outbreak meant people admitted to hospital were exposed to the virus as it spread among staff and patients.

The full scale of this transmission has been explored in a new nationwide study which shows that, up to 1 August 2020, an average of 11.3 per cent of patients with Covid-19 in UK hospitals had been infected after admission.

This proportion may have reached as high as 19.6 per cent in the middle of May, long after the UK had passed its first peak, research from the UK’s Isaric programme shows.

Out of a total of 82,624 people who received hospital treatment for Covid, between 5,699 and 11,862 are suspected to have caught the virus while on a ward.

However, the scientists behind the study, published in The Lancet, said this is likely to be an underestimate “as we did not include patients who may have been infected but discharged before they could be diagnosed”.

Researchers identified patients who were infected in hospital using a combination of their admission date and symptom onset date, and estimates of the date they were first exposed to the virus based on its known incubation period.

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

There was also notable variation in the rate of hospital-acquired infection (HIA) between different healthcare settings, the research showed, pointing to the different standards of infection control that were implemented in each NHS trust.

“There were some outstanding example of good infection prevention control practice, and there were some examples where that was not good,” said Calum Semple, a professor in child health and outbreak medicine involved in the study.

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

The researchers said the variation between hospital settings “requires urgent investigation” to ensure measures can be put in place to implement best practices to reduce infection.

During the first wave, some trusts in England were disciplined by the care watchdog for failing to properly enforce infection control measures, which led to significant outbreaks in cases.

East Kent Hospitals University Trust had almost twice the national rate of hospital-acquired infections of Covid-19 between 30 June and 26 July,

Prof Semple said the overall average HIA rate of 11.3 per cent was similar to that which is usually seen during seasonal or pandemic flu outbreaks, but he admitted the variation in standards between hospitals was “surprising”.

“You’ll see there were hospitals that had between a 1,000 and 2,000 patients, these are your busiest hospital, and actually the majority of them had lower than average hospital acquired infection rates,” he said.

“There are clearly some hospitals that are big, busy and have really nailed infection prevention control. So there’s lessons to be learned from what they were doing so well that a smaller, quieter hospital should have probably been able to do.”

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 were a number of reasons why patients had caught Covid while in hospital.

“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.”

The rates of HIA are now “at much lower levels”, sitting “somewhere between 2 per cent and 5 per cent”, said Prof Semple. This is despite the spread of the highly infectious Delta variant, which is now dominant in the UK.

They explained that improved infection control practices, along with the use of PPE and side rooms in hospitals, have considerably reduced the risk of HIA.

However, more needs to understood about Covid-19 transmission in hospitals in preparation for the winter months, the scientists said.

“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,” Dr Green added.

“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.”

Other estimates of HIA in England point to much higher rates than the Isaric study. As first reported by The Independent, internal NHS data showed 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.