Tens of thousands of new cases of coronavirus in the UK are not being included in the official daily figures, analysis suggests.
An average of 114,600 new cases were recorded each day in the week to December 23, according to the Government’s Covid-19 dashboard.
But the true figure might have been more than three times that number, according to new estimates published by the Office for National Statistics (ONS).
It means more than one and a half million new cases of coronavirus could have been missed from the official figures in the week before Christmas.
High levels of underreporting will still be affecting the Government’s daily figures, meaning the current volume of cases in the UK is unclear.
The ONS has published the data as part of its weekly infection survey, which estimates both the overall prevalence of the virus across the country and the number of new cases.
All estimates are based on analysis of nose and throat swabs taken from a representative sample of more than 150,000 people in private households.
They show there were an estimated 357,600 new cases of Covid-19 each day in the week to December 23, more than three times the 114,600 recorded on the Government’s dashboard.
And in the seven days to December 17, the ONS estimated 221,200 new cases in the UK – nearly three times the number on the dashboard, which was 80,400.
The huge difference in totals shows just how many new cases of Covid-19 are likely being missed in the Government’s daily figures, which count only those people who have reported themselves as having tested positive for the virus.
This means the figures are affected by factors such as how many people are coming forward for tests, have chosen to report their test results, or who are taking a test because they know they have coronavirus symptoms.
The ONS survey gets round this by sampling the same number of people in the UK every week, regardless of whether they know they have Covid-19 or have reported a positive result.
Kevin McConway, emeritus professor of applied statistics at the Open University said the ONS survey is a “more reliable source of information” than the Government’s dashboard because “it isn’t affected by changes in the numbers and types of people being tested routinely, or in availability of tests”.
He said: “A large proportion of new infections is not picked up by the routine testing that provides the dashboard numbers. Also, the ONS estimates can take into account reinfections. The dashboard case figures do not currently count anyone as a case if they have previously been counted as a case, so reinfections are excluded.
“That’s a potential problem with Omicron because there is evidence that it is considerably more likely to infect previously-infected people than was the case for previous variants.”
There is a lag of several weeks between the period covered by the ONS survey and the publication of the figures due to the time needed to collect and process the data.
This means an estimate of the likely true number of new cases of Covid-19 in the UK over Christmas and the new year won’t be known until the end of January.