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There is a 'very real chance' the NHS will face unsustainable pressure in the South West as workers must offer 1.7 million booster jabs in just over two weeks, health bosses have said.
The warning comes as the Omicron strain of coronavirus continues to spread quickly across the region.
Health workers must now aim to offer booster jabs to all eligible adults by the end of December, with some non-essential appointments being postponed to free up staff.
Dominic Mellon, Deputy Director of UKHSA (UK Health Security Agency) for the South West, said there are currently 250 confirmed cases of Omicron in the region.
But, he added, there are more than 600 unconfirmed cases, and it is believed the true number could be much higher.
Cases of the new strain in the South West are doubling every 2.5 to three days, said Mr Mellon, which suggests the variant is more transmissible than any other previous one.
"It's rapid and it's frightening and it's going to get worse rather than better," he said.
The speed of transmission combined with the difficulties of getting hold of lateral flow tests worries Dr Simon Bradley, a GP from Little Stoke in South Gloucestershire.
He says there is a pattern of "a lot of is people repeating their lateral flow if it's positive," and taking the LFTs if they are symptomatic - both are wasteful ways to use the tests.
Pharmacists are also calling for people not to stockpile the tests.
Safia Latifa, a pharmacist in Clifton, says they are supposed receive up to 100 test packs a day but they are snapped up quickly as "even half of that amount is gone within an hour".
The key advice from the region's health bosses is for every eligible adult to get their booster jab as soon as possible - and for people to take lateral flow tests before going out and mixing with people over Christmas.
While they said they want people to enjoy themselves over the festive season, Dr Michael Marsh, NHS England's Medical Director, said it is "not the time to take high risks" and people must think about their own personal safety.
"We urge everybody who is able to book their jab to come forward and do so - it is the best defence we've got," said Professor Debbie Stark, Regional Director for Public Health England South West.
Meanwhile Professor Adam Finn, from the University of Bristol and a member of the Joint Committee on Vaccination and Immunisation (JCVI), told BBC Breakfast the wave of Omicron is just taking off across the country.
He said: “The wave is coming very fast and in fact alarmingly fast – if anything faster than ever. So it really is a race at the moment.
“The more immunity that we’ve all got the less of a problem this is going to be, but I’m afraid it is going to be a serious problem either way.”
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Prof Finn said it is not up to him to say what regulations should be put on the population, but added: “I think I can certainly encourage people to do everything they can to minimise spread of the virus during this critical period and, of course, a lot of that can be done voluntarily without anyone imposing rules on people.
“We all know now what the things are that we can do. We can avoid social contact, we can minimise contact at work, we can wear masks and really importantly, do lateral flow tests and check that you aren’t showing signs of infection on a test before you go into a crowded place where you might infect other people.”
Prof Finn said he is “very concerned” about the current number of daily infections, adding that we are “going to see the numbers of people becoming ill and needing hospital care beginning to rise steadily now over the next week and maybe over Christmas as well.”
But he said boosters take effect in the body quickly, adding: “It does come through very fast because you’ve got immunological memory, you’ve seen the antigen before from your previous doses, so the level of protection goes up pretty quick.”