Stopping Covid spreading in hospitals could have made ‘substantial reduction in first wave deaths’

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Stopping the spread of coronavirus in hospitals could have led to a ‘substantial’ reduction in the number of deaths in the first wave, SAGE research has suggested.

A paper presented to the government advisory board found that as many as 40 per cent of hospital patients with Covid caught it after they were admitted.

And this spread between patients and hospital staff meant that the first phase of the epidemic was ‘prolonged, potentially by several weeks’, they said. 

The spread of the virus on wards has been a problem for the NHS throughout the crisis, with hospitals that have more Covid patients finding it harder to manage. Although staff must wear protective equipment at all times and Covid and non-Covid patients are segregated, the virus still spreads from people who don’t have any symptoms or who get false negative test results. 

The SAGE paper, published today, suggested that as many as 36,152 of around 90,000 people who were diagnosed with the virus in hospital between February and July 2020 had caught it in hospital.

Preventing the spread inside hospitals, the researchers said, could have had a ‘substantial’ impact on deaths because the patients were often old or frail. 

Based on the 22 per cent hospital death rate the NHS saw in the first wave up to July 26, 2020, this extra 36,152 cases could have led to 8,062 fatalities that may have been avoided if in-hospital transmission could have been stopped.  

It is too soon to know whether in-hospital transmission was reduced in the second wave, with 24,000 people still on wards with Covid-19 across the UK. The latest NHS England data suggests that around one in five hospital cases is acquired on a ward – an average of 328 per day out of 1,689 in total over the week to February 10.

The paper estimated that at least 8.8 per cent of Covid-19 hospital cases in England over the first wave of the pandemic may have been what are known as nosocomial, or hospital-acquired, infections.

These include people who became ill while an inpatient for another condition, or who developed Covid-19 shortly after being discharged and then ended up back in hospital. 

Some of the cases were only suspected, while others were confirmed by process of elimination. 

The 8.8 per cent figure was for people who tested positive 15 or more days after being admitted, who were certain to have caught the virus in hospital.

But as the criteria were broadened, the proportion of people whose illness could be traced back to a hospital stay got significantly higher.

Including people testing positive after eight days or three days if they had been recently discharged from hospital, it doubled to 18.3 per cent; one in five. Those people were considered highly likely cases of in-hospital infection.

When the three-to-seven days group with no recent hospital stay was included it was 25.9 per cent, and when all of the above were combined with people who had recently been to hospital and tested positive on day two of their second stay, it rose to 40.5 per cent.

The latter groups were the least likely to have caught the virus in hospital but the risk was still high enough for them to be counted as possibles.

Medical workers travelling in and out of the hospital every day unavoidably raises the risk of this transmission, and the risk of it spilling out into the community, although this wasn’t studied in the paper. 

The paper said that while the proportion of the total Covid-19 cases linked to hospital transmission was large, it was relatively small in terms of the entire outbreak.

Because so many of them were likely to have been vulnerable people, however – and hospital patients have a significantly higher death rate than the general population – the in-hospital spread may have killed thousands of extra people.

The undated document said: ‘A simple calculation assuming five per cent of infections are hospitalised and of these hospital cases, if 25 per cent are due to nosocomial infection, the complete prevention of nosocomial transmission would have led to approximately one per cent impact on the number of infections in the English epidemic overall.

‘However, since hospitalised patients tend to be old and/or frail, the impact in terms of morbidity and mortality would nonetheless be expected to be substantial.’ 

The paper also warned that the risk of in-hospital transmission was that it would spill out into the community, and that this was making the outbreak go on for longer. 

It added: ‘An exploration… shows little impact of nosocomial transmission initially, but in the last quarter of the first wave the impact of nosocomial transmission may have been to prolong the epidemic, potentially by several weeks.’

The explanation for this was that people were being discharged from the hospital while still infectious, passing it on to others.

Staff would also inevitably be more likely to catch the virus if more patients were carrying it, and they would then take it home to their families. 

The study said: ‘A number of the nosocomially infected patients will be discharged and lead to onward community transmission.

‘Modelling this onward transmission crudely, with a time-varying R, up to the fourth generation of transmission, gives 50,550 onward infections.

‘A proportion of these infections will progress to disease and subsequently be hospitalised.’ 

Hospitals are still under pressure from large numbers of Covid-19 patients, although there are around 10,000 fewer people needing medical care than at the peak of the second wave in January.

Researchers predict that the impact of the country’s mass vaccination programme won’t feed through into a decline in admissions to hospital until the second half of March, when they should have fallen by two thirds, with intensive care patient numbers down 36 per cent.

A study published last night by Professor Tim Cook, a doctor in Bath and researcher at the University of Bristol,  claimed the benefits of vaccination may already be reducing the death toll by as much as 10 per cent, but this is difficult to see in data because lockdown is also bringing the numbers down. 

The impact of vaccines will affect age groups in reverse order – the same order they are vaccinated in – which dictates the data that will show changes first.

The average age of people dying from Covid is 83, the team said, while hospital patients are 73, on average, and intensive care patients 61. 

When everyone over 60 has had a vaccine, deaths could be reduced by a staggering 96 per cent, with hospitalisations down 80 per cent.

Professor Cook and colleagues said: ‘The impact of vaccination on deaths due to Covid-19 will be much more rapid than the impact on hospital and ICU adissions. 

‘Our model suggests that the impact of vaccination on daily deaths due to Covid-19 will be substantial throughout February and March. 

‘The impact of vaccination on hospital and ICU admissions will initially be slower: these will not decrease substantially until late March, with reductions continuing throughout April.’