UK researchers have developed a calculator to identify those at highest risk of severe illness from Covid despite having one or two vaccines.
They say jabs provide protection against serious illness and death for most people, but for some the risks – while much lowered by jabs – remain.
This includes older people, people with Down’s Syndrome, and those with weakened immune systems.
The risks are highest for those who have not been fully vaccinated.
Writing in the BMJ, scientists say those at risk should ensure they have both jabs.
They suggest their risk calculator could be used to help spot fully vaccinated individuals who may additionally benefit from boosters or early treatment – including newer therapies such as monoclonal antibodies.
The research team – which includes scientists from the universities of Edinburgh, Oxford and Nottingham – examined hospital records involving some five million people in England who had had two jabs and about two million who had had one.
There were about 2,000 deaths linked to Covid and almost the same number of Covid hospital admissions – most occurred 14 or more days after the first vaccine (when substantial immunity is expected to have developed).
Just 81 deaths and 71 admissions happened 14 or more days after the second vaccine dose.
From this data, the groups most at risk of severe illness or death, included:
Researchers say while overall the risks would be lower for people who have had two jabs, they would expect the general pattern to remain in terms of the groups identified to be at higher risk.
But they say because there were relatively few Covid-related hospital admissions and deaths in people who had two jabs it was harder to build up a precise picture.
And they say certain risks – such as people who do high-risk jobs – could not be taken into account.
Prof Julia Hippisley-Cox, from the University of Oxford, said: “Individual risk will always depend on individual choices as well as the current prevalence of the disease. However we hope that this new tool will help shared decision making and more personalised risk assessment.”
The risk calculator is available online for academic use and there are plans to make a version that will be available to the public.
An earlier version of the risk calculator helped spot people who would benefit from shielding in England.
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