Death rates for patients admitted to hospital with severe Covid-19 dropped by around half between March and the end of June, according to new research.

The study of more than 21,000 hospital admissions in England found significant drops in deaths for patients admitted to both high dependency units and intensive care.

Experts from the University of Exeter, supported by the University of Warwick and the Alan Turing Institute, found that death rates  – based on survival 30 days after admission – were highest in late March, at 26% among people admitted to high dependency units, and 41% among those admitted to intensive care.

But by the end of June, these figures had dropped to 7% and 21% respectively.

The team, writing in the journal Critical Care Medicine, said: “There has been a substantial improvement in survival amongst people admitted to critical care with coronavirus disease 2019 in England, with markedly higher survival rates in people admitted in May and June compared with those admitted in March and April.”

Dr John Dennis, of the University of Exeter Medical School, who led the research, said: “Importantly, we controlled for factors including age, sex, ethnicity and other health conditions such as diabetes.

“This suggests the improvement in death rates in more recent months is not simply due to younger, or previously healthier, people being admitted to critical care.

“A number of factors are likely to be at play here, including improved understanding of how to manage Covid-19 amongst doctors, and the introduction of effective treatments.”

The team accessed national data from adults admitted to critical care via the Covid-19 Hospitalisation in England Surveillance System (CHESS).

The data included 108 critical care units.

Dr Bilal Mateen, of the University of Warwick, said: “The reduction in the number of people dying from Covid-19 in hospitals is clearly a step in the right direction, but it’s important that we do not become complacent as a result.

“It’s possible that the higher death rates at the peak of the pandemic are in part because hospitals were so overcrowded at that point.

“Even at the lowest point, nearly a quarter of admissions to intensive care were still dying– that’s a huge number of people, and we have to do all we can to control the spread of the virus and keep hospital admissions as low as possible.”