Health bosses were on Monday night accused of misleading ministers in an attempt to justify Covid rules which have crippled the country, with isolation now expected to be cut to five days.
The UK Health Security Agency, run by Dame Jenny Harries, on Monday admitted it was wrong to claim England’s isolation rules were effectively in line with other nations, including the United States.
Its rationale had been repeatedly cited by ministers as they rebuffed calls to cut isolation from seven to five days in order to tackle major staffing crises across most sectors.
Sajid Javid, the Health Secretary, was said to be "frustrated" by the situation, with Downing Street and ministers including Rishi Sunak, the Chancellor, only becoming aware of the discrepancy on Monday.
It now looks all but certain that the guidance will be changed and people asked to isolate for five days after Boris Johnson put pressure on scientists to look again at the matter.
On Monday, Mr Johnson said ministers were considering reducing the self-isolation period for fully vaccinated people who test positive for Covid. Mr Javid is among those understood to be keen to see such a move.
The Prime Minister’s spokesman said the UKHSA would be leading a review of the evidence, saying: "If it’s possible to go further, we will do so." Until now, it has rebuffed calls to reduce isolation to five days in line with the United States, insisting this was "not comparing like with like".
A central argument put forward by officials and cited by ministers was that the isolation period in the USA begins later, as it depends on a positive result.
On Monday the UKHSA admitted this was factually incorrect, with both countries in fact counting the isolation "clock" from the point of symptoms unless cases are asymptomatic.
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Mr Johnson signalled his determination to address the matter after a number of Cabinet ministers called for changes to be made.
Speaking to broadcasters during a visit to a vaccination clinic in Uxbridge, he said there was an "argument to be had about the quarantine period – whether to come down from seven days to five days", adding: "The thing to do is to look at the science. We are looking at that, and we will act according to the science."
Last week, ministers repeatedly defended the current isolation period of seven days as long as a lateral flow test is negative, saying they were following "the clinical evidence" from the UKHSA.
They cited a blog by the organisation, which was corrected on Monday. In the article, published more than a week ago, officials said: "There have been calls for us to also shorten our self-isolation window in line with the United States guidelines of five days.
"However, it is important to note that we are not comparing like with like. In the UK, our advice is to self-isolate from the point at which you have symptoms or get a positive test, whichever is first – this is when the self-isolation ‘clock’ starts. In the United States, the advice is to isolate for five days once you get a positive test, which may be some days after the first symptoms."
The message was corrected after the US Centers for Disease Control (CDC) said isolation begins when symptoms appear – as it does in the UK.
The CDC first published guidance on cutting isolation to five days on Dec 27. But Monday’s changes to the UK guidance were only made almost a week after it published more detailed information on Jan 4, explaining that, for those without a test result, the clock started with the appearance of symptoms.
The amended piece says: "In the UK, our advice is to self-isolate from the point at which you have symptoms or get a positive test, whichever is first – this is when the self-isolation ‘clock’ starts. In the United States, the advice is to isolate for five days also from this point."
Both blogs justify the current position, which means isolating for a minimum of seven days, on the grounds that between 10 and 30 per cent of people are still infectious on days five and six. But neither explains why the remainder of those isolating should not be freed on day five if their lateral flow tests are negative.
Downing Street and Cabinet ministers were caught unaware by the UKHSA’s change. Mr Sunak is understood to have become aware of the discrepancy after conversations with Americans and raised concerns at an internal meeting on Monday, while Mr Javid was said to be "frustrated".
"It is not ideal that the advice wasn’t correct, but these things happen," said a source close to another Cabinet minister who had repeated the UKSHA position.
Dame Jenny was recently accused of disseminating misleading information that inflated the risks of the omicron variant, saying the lag between cases and hospitalisations would not be known for 17 days, when the lag is widely agreed to be 10.
No date has been set for when the seven-day self-isolation rule will be cut. The final go-ahead will be dependent on scientific advisers saying that the reduction is a safe course of action, and in particular that it will not trigger a new spike of virus infections.
A senior government source said: "We need to make sure the policy we end up with is robust and won’t lead to a problem of many more people leaving isolation too early and spreading Covid."
The current rules were drawn up just before Christmas, with 10 days replaced by a minimum of seven, with exit from it depending on a negative test on day six and seven. The changes were first made in England, followed by Wales, Northern Ireland and Scotland.
One Whitehall source said Mr Javid "wants to see the fewest days possible and is open to five days if clinicians can recommend it as being safe to do so". Another said: "It feels more like a question of when the change will be made, rather than if."
They said UKHSA’s review of the evidence, examining transmission rates on day five, would be set against other economic and social considerations.
Another source said: "It’s definitely a moveable feast – it depends on a lot of different factors, and the levels of Covid in circulation. There is a balancing act between the risks of transmission and the need to get people back to work."
Several ministers have called for changes in recent days, with Nadhim Zahawi, the Education Secretary, saying on Sunday that cutting isolation would be "very helpful" in dealing with staffing crises.
A spokesperson for the UKHSA said: "We updated our blog following clarification from the CDC on their isolation guidance on 4 January. Our current guidance of releasing individuals from isolation on day 7 with two negative lateral flow test results taken 24 hours apart has a low risk of an individual being released infectious – similar to the risk of being infectious after 10 days isolation. In the US people are asked to isolate for 5 full days, in the UK the advice is to isolate for 6 full days."