New tool identifies groups most at-risk from Covid after vaccination

The immunosuppressed and those with dementia, Parkinson’s or chronic disorders such as kidney disease are still at a greater risk of hospitalisation or death from Covid after vaccination compared to the rest of the population, new research shows.

The QCovid tool developed by scientists at the University of Oxford shows that while the risk of severe Covid-19 after vaccination remains low, some people remain more vulnerable than others.

Age continues to be a “major risk factor”, the experts said, with older vaccinated individuals more likely to end up ill from Covid compared to their younger counterparts.

Those from Indian and Pakistani backgrounds who are vaccinated face the highest risk among ethnic groups.

People living with chronic conditions such as Down’s syndrome, kidney disease, sickle cell disease, HIV/Aids and liver cirrhosis are also at more risk of severe disease or hospital admission after vaccination.

The new algorithm behind the QCovid tool, which was first developed in 2020 and helped influence policy on shielding, predicts those most at risk of serious Covid-19 outcomes from 14 or more days after second vaccination dose, when substantial immunity is expected to have developed. The findings do not take into account the different types of vaccines received by people.

Researchers at the University of Oxford used national linked datasets from general practice, national immunisation and Sars-CoV-2 testing, death registry and hospital episode data.

A sample of more than 6.9 million vaccinated adults was analysed, of whom 5.2 million had both doses – representative of the UK population as a whole. This sample included 2,031 Covid deaths and 1,929 Covid-related hospital admissions, of which 81 deaths and 71 admissions occurred 14 or more days after the second vaccine dose.

Based on this, the researchers have developed cumulative scores to calculate people’s risk of hospital admission or death from Covid-19 following one or two vaccination doses.

The scores take into account factors including age, sex, ethnic group and the background rate of Covid infections.

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."

Commenting on why other ethnic groups may have dropped off in terms of being at risk, Professor Aziz Sheikh, of The University of Edinburgh and a co-author of the paper, published in the British Medical Journal, said it may be due to social reasons.

He explained: “I think the fact that some of the ethnic variations are diminishing suggests that a lot of this was because it’s socially patterned – perhaps because of occupational risk considerations etc.

“I think with the two subgroups that remain, this is speculative, but these groups – the Indians and Pakistanis – do tend to have slightly higher household sizes and so there may be that kind of within household transmission going on.”

Penny Ward, a visiting professor in pharmaceutical medicine at King’s College London, said most of the people at higher risk of an adverse outcome “may be expected to increase their antibody response when given a booster dose”.

In some cases, though, such as with the immunocompromised individuals, the risk posed by Covid may continue to linger – even after vaccination.

These people, she said, “would potentially benefit from the available monoclonal antibody treatments becoming available, to prevent infection post exposure, or, if unwell, to early treatment to prevent more severe disease”.