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Tool identifies vaccinated groups at highest risk of severe COVID-19

Published: 20 September 2021

A tool developed by NIHR-funded researchers has been shown to accurately identify people who are at greatest risk from severe COVID-19 despite being fully vaccinated.

Research on the QCovid® tool has found that it can identify vaccinated people who are at greatest risk of hospitalisation or death from severe COVID-19 14 days after their second vaccine dose, when substantial immunity should be expected.

The QCovid® risk prediction tool, developed in 2020 by researchers from the University of Oxford, has been previously shown to accurately estimate a person’s risk of becoming seriously ill due to COVID-19. The tool was then used to guide shielding policy decisions in February 2021.

For this new research, published in the British Medical Journal, the researchers used data from over 6.9 million vaccinated adults, 5.2 million of whom had received both vaccine doses. The data were drawn from national linked datasets from general practice, national immunisation and SARS-CoV-2 testing, death registry and hospital episode statistics.

The researchers used these data to develop cumulative risk scores to calculate people’s risk of hospitalisation or death from COVID-19 following one, or two vaccination doses. These risk scores take into account a range of factors including age, sex, ethnic group and the background rate of COVID infections.

Their analysis highlighted an elevated risk of severe COVID-19 in vaccinated people who:

  • are immunosuppressed as a result of chemotherapy, a recent bone marrow or solid organ transplant, or HIV/AIDS
  • have a neurological disorder, including dementia and Parkinson’s
  • are resident in a care home
  • have a chronic disorder, including Down’s syndrome.

The researchers hope that their tool can be used in a variety of health and care settings to inform those more likely to be at risk, and potentially help to prioritise those identified for further trials of vaccines, boosters or future preventative therapies.

Professor Julia Hippisley-Cox, Professor of Clinical Epidemiology and General Practice at the University of Oxford and co-author of the paper, said: “The UK was the first place to implement a vaccination programme and has some of the best clinical research data in the world.

“We have developed this new tool using the QResearch database, to help the NHS identify which patients are at highest risk of serious outcomes despite vaccination for targeted intervention. This new tool can also inform discussions between doctors and patients about the level of risk to aid shared decision making.”

The researchers report that there were relatively few COVID-19 related hospitalisations or deaths in the group who had received the second dose of any vaccine, meaning that the study lacked the statistical power to determine if the groups listed above are more, or less, at risk following a second vaccine dose compared with following the first dose.

Furthermore, they did not distinguish between type of vaccination offered, and acknowledge that their study may have been limited by factors such as exposure to the virus (for example, occupation is not often recorded in general practice or hospital records).

Professor Aziz Sheikh, Professor of Primary Care Research & Development and Director of the Usher Institute at The University of Edinburgh and a co-author of the paper, said: “This enormous national study of over 5 million people vaccinated with two doses across the UK has found that a small minority of people remain at risk of COVID-19 hospitalisation and death. Our risk calculator helps to identify those who remain most at risk post-vaccination.

“Our new QCovid tool, developed with the help of experts from across the UK, has been designed to identify those at high risk who may benefit from interventions such as vaccine booster doses or new treatments such as monoclonal antibodies, which can help reduce the risk of progression of SARS-CoV-2 infection to serious COVID-19 outcomes.”

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