One in two hospitalised COVID-19 patients develop a complication

An observational study of more than 70,000 people in 302 UK hospitals has found that one in two people hospitalised with COVID-19 developed at least one complication.

The new study, published in The Lancet, is the most comprehensive of its kind and the first to systematically assess a range of in-hospital complications, and their associations with age, sex and ethnicity, and their outcomes for the patients.

Most common complications included renal, complex respiratory, and systemic complications, but cardiovascular, neurological and gastrointestinal and liver complications were also reported.

The authors, including researchers from the University of Liverpool, say these complications are likely to have important short- and long-term impacts for patients, healthcare utilisation, healthcare system preparedness, and society amidst the ongoing COVID-19 pandemic. They also note that these complications are different to long COVID symptoms in patients with COVID-19 who were not hospitalised.

The authors say that complications in patients admitted to hospital with COVID-19 are high, even in young, previously healthy individuals – with 27% of 19-29 year olds and 37% of 30-39 year olds experiencing a complication. They also note that acute complications are associated with reduced ability to self-care at discharge – with 13% of 19-29 year olds and 17% of 30-39 year olds unable to look after themselves once discharged from hospital.

The study looked at cases between 17 January and 4 August 2020 before vaccines were widely available, and new variants of the virus had not arisen. However, the authors note that their findings remain relevant in dispelling suggestions that COVID-19 presents no risk to younger healthy adults, many of whom remain unvaccinated.

The authors warn that policymakers must consider the risk of complications for those who survive COVID-19, not just mortality, when making decisions around easing restrictions.  The authors predict that COVID-19 complications are likely to cause significant challenges for individuals and for the health and social care system in the coming years.  Policy makers and health-care planners should anticipate that large amounts of health and social care resources will be required to support those who survive COVID-19.

Chief Investigator and joint senior author of the study, Professor Calum Semple, University of Liverpool, UK, says: “This work contradicts current narratives that COVID-19 is only dangerous in people with existing comorbidities and the elderly. Dispelling and contributing to the scientific debate around such narratives has become increasingly important. Disease severity at admission is a predictor of complications even in younger adults, so prevention of complications requires a primary prevention strategy, meaning vaccination.”

Joint senior author Professor Ewen Harrison from the University of Edinburgh, UK, says: “Patients in hospital with COVID-19 frequently had complications of the disease, even those in younger age groups and without pre-existing health conditions. These complications could affect any organ, but particularly the kidney, heart and lungs. Those with complications had poorer health on discharge from hospital, and some will have long-term consequences. We now have a more detailed understanding of COVID-19 and the risks posed, even to younger otherwise healthy people.

He adds: “Our review highlights some insightful patterns and trends that can inform healthcare systems and policy maker responses to the impacts of COVID-19. Our results can also inform public health messaging on the risk COVID-19 poses to younger otherwise healthy people at a population level, particularly in terms of the importance of vaccination for this group.”

Previous research on the impact of COVID-19 on patients has focussed on the numbers of deaths or on outcomes related to one specific organ system or health condition. The new study assessed in-hospital complications in adults aged 19 years or over with confirmed or highly suspected SARS-CoV-2 infection leading to COVID-19 disease.

56% of those included in the study were men, 81% had an underlying health condition, 74% were of white ethnicity, and the average age of the cohort was 71 years. Almost one in three participants (32%, 23,092 of 73,197) in the study died.

Overall, complications occurred in 50% of all participants, including in 44% of participants who survived.

The incidence of complications rose with increasing age, occurring in 39% (3,596 of 9,249) of 19-49 year olds, compared to 51% (32,771 of 63,948) of people aged 50 and older. Complications were more common in men compared with females, with males aged older than 60 years the most likely group to have at least one complication.

People of white, South Asian, and East Asian ethnicities had similar rates of complications, but rates were highest in Black people (58% in Black patients vs 49% in white patients).

The authors note some limitations, including that the data does not provide a long-term picture, and that the timings of complications and patients quality of life were not studied. In addition, the complications in the study were predefined and not specific to COVID-19, so may underestimate some areas as these were added later. In addition, as it was inappropriate to subject patients to numerous tests, patients did not undergo additional tests for complications, and the authors say that the true burden of complications is likely to be higher.

Co-author Professor Jonathan Van Tam said: “The ISARIC/CO-CIN study was set up at very short notice in March 2020. Ever since it has delivered a steady stream of high-quality data to the UK’s SAGE committee and the Department for Health and Social Care on patients hospitalised with SARS-CoV-2 infection. The project has also produced a series of highly important peer-reviewed science papers which have been heavily cited and are of benefit to scientists worldwide. This is another example of how with support from the UK’s National Institute for Health Research, the NHS has delivered high quality clinical science studies at pace.”

Dr William van’t Hoff, Chief Executive of the NIHR Clinical Research Network said: “This study has provided important data to support our understanding of complications arising as a result of severe COVID-19 – including identification of groups most at risk of complications from this dreadful disease. The work, performed in the first phase of the pandemic, underlines how serious COVID-19 is and reinforces the importance not only of the treatments now available, but critically, the role of vaccination in reducing infection and lessening its impact.  It also emphasises the need for further research into short and long-term health implications for patients hospitalised with the disease.”

The study was funded by the National Institute for Health Research (NIHR) and the UK Medical Research Council. It was conducted by researchers from University of Edinburgh, University of Liverpool, University of Sheffield, University of Glasgow, University of Oxford, Public Health England, University of Nottingham, Department of Health and Social Care, and Imperial College London.

The full study can be found here: