There is insufficient evidence that a reduction in the Covid self-isolation period from seven days to five would not cause a surge in coronavirus infections, an NHS boss has suggested.
Under current rules in England, people who receive negative lateral flow results on days six and seven of their self-isolation periods - with tests taken 24 hours apart - no longer have to stay indoors for a full 10 days.
But there are mounting calls for the government to cut this further as staff self-isolations are putting businesses and the NHS under severe strain.
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These calls have gained momentum after US health officials halved the recommended isolation time for those with asymptomatic Covid from 10 to five days.
The US Centers for Disease Control said most transmission of the virus happens in the two days before and three days after symptoms develop.
However, while acknowledging staff absence is currently a major issue for the health service, Matthew Taylor, chief executive of the NHS Confederation, said there is insufficient data to follow the American example.
Speaking to BBC Radio 4’s Today programme, Mr Taylor suggested he had not seen a process where the evidence on cutting isolation could be assessed.
He said: “The government, with scientific advice, has to make an assessment of the balance of risk here, but it’s important to recognise that there are risks to anything that we do, and if we were to reduce to five days that would have to be based on very clear evidence that is not going to increase the rate of infection.”
He pointed to Omicron being a new variant and the fact that Covid hospital admissions are still rising, though the number of Covid patients needing ventilators is down.
NHS data shows 8% of Covid patients in England on Tuesday were in beds requiring ventilators, compared with 13% at the start of the month.
Across the UK, some 842 people with Covid were in ventilator beds on December 22, compared to a peak of 4,076 on January 22.
“It’s also important to recognise the hospitals are full of people who are very vulnerable and, for those people, even a relatively mild form of the virus can have serious consequences, so whilst anyone in the NHS would be delighted if people were able to come back to work earlier, if they are safe, we need to be absolutely sure that that is the case,” Mr Taylor added.
Labour has also said the government should avoid “rushing into” cutting Covid isolation times.
"These decisions should always be driven by the advice of the chief medical officer and the chief scientific adviser," shadow work and pensions secretary Jonathan Ashworth said.
"I would leave it to them to give us their judgement on this."
He said that ministers needed to ensure people can get hold of lateral flow tests - which are running in short supply in some areas - so they can be released from isolation after negative results.
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NHS Providers boss Chris Hopson, meanwhile, has said many in the health service now fear staff shortages caused by people isolating could represent a “bigger challenge” than the number of patients needing treatment for Covid.
These staff shortages have coincided with warnings from UK pharmacies that a lack of lateral flow tests is causing a “huge” problem as people have been requesting them so regularly over the Christmas period.
Leyla Hannbeck, chief executive of the Association of Independent Multiple Pharmacies, said the current daily supply of almost 900,000 lateral flow tests is not enough to meet demand.
On Tuesday, the UK recorded its highest ever number of confirmed daily Covid-19 cases as the Omicron variant continued to spread across the country. A further 129,471 lab-confirmed cases were recorded in the UK, the government said, breaking the previous record of 122,186 cases reported on Christmas Eve.
But despite the soaring figures, Health Secretary Sajid Javid said there will be no new restrictions before the new year in England, in contrast to tighter curbs in place for the devolved administrations.
Some experts have said it is better to intervene and overreact now than to let social mixing go unrestricted and end up with higher death and hospitalisation numbers.
The government, however, has stressed that data is constantly being kept under review, while it continues promoting booster vaccinations in a bid to tackle the rising cases.
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On Wednesday, the prime minister said the government had assessed the "balance of the risks" in the decision-making process.
He explained: "We see the data showing that, yes, the cases are rising and, yes, hospitalisations are rising, but what is making a huge difference is the level of booster resistance or level of vaccine-induced resistance in the population."