The number of COVID reinfections is rising rapidly in people over the age of 30, a UK Health Security Agency (UKHSA) expert has warned.
According the latest UKHSA data, at least 268,517 people had had COVID more than once in England by the end of December.
Epidemiologist Meaghan Kall said the figure is likely to be a significant underestimate due to limited testing in the first coronavirus wave, adding that more data is needed to understand whether reinfections are milder.
In a series of tweets, Kall said reinfections started rising in the under 30s when the Omicron wave first hit, but are now rising in those aged over 30.
The omicron variant's ability to evade previous immunity means around one in 10 new COVID-19 infections are in people who have previously had the virus, she added.
In December, a report from Imperial College London suggested that the risk of reinfection with Omicron is more than five times higher than with the previous Delta variant.
Currently, the UK's daily COVID data does not include reinfections, leading to calls to change the system.
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Professor Sir David Spiegelhalter, a statistician at the University of Cambridge, told the Guardian: "The reinfection rate was fairly low with Delta, but is higher now, both because prior infection provides little protection against Omicron, and there is a bigger pool of people with prior infection."
So far, Boris Johnson has steered away from imposing fresh restrictions to tackle the wave of Omicron cases, sticking with Plan B measures amid warnings that the NHS is at breaking point.
Earlier this week, as daily confirmed COVID cases in the UK exceeded 200,000 for the first time, the prime minister acknowledged that parts of the NHS would feel "temporarily overwhelmed", but said current guidance for people to wear masks and to work from home, as well as COVID passes, would help "ride out" the latest wave of infections.
However, Johnson is facing warnings that the NHS is at breaking point.
On Friday it emerged that the army is preparing to further support the NHS through the current wave of COVID-19, NHS data showing that staff absences due to COVID have risen 59% in a week.
Some 39,142 NHS staff were off sick due to COVID reasons on 2 January.
Around 200 army personnel have already been drafted in to help the NHS in London.
NHS national medical director Professor Stephen Powis said rising Omicron cases were “piling even more pressure” on hospital trust workers.
He said: “Omicron means more patients to treat and fewer staff to treat them.
“In fact, around 10,000 more colleagues across the NHS were absent each day last week compared with the previous seven days and almost half of all absences are now down to COVID.
“While we don’t know the full scale of the potential impact this new strain will have, it’s clear it spreads more easily and, as a result, COVID cases in hospitals are the highest they’ve been since February last year – piling even more pressure on hard-working staff."
Patricia Marquis, the Royal College of Nursing’s director for England, said: “Outside of healthcare, staffing shortages are closing shops and cancelling trains but nurses can’t stop helping their patients.
“Instead, they find themselves spread thinner and thinner, but they can’t keep spinning plates indefinitely either – this situation is simply not safe.”
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