The UK appears to have passed the peak of the Omicron wave after new figures showed that weekly nationwide infections have dropped by almost one million.
A total of 3.4 million Britons were estimated to be infected with Covid in the seven days to 15 January, according to the Office for National Statistics (ONS) - down from 4.3 million in the previous week.
It is the first week that the ONS’ weekly Covid report, seen as the gold standard for predicting the scale of the UK epidemic, has recorded a drop in case since Omicron first took hold in late November.
The figures come as prime minister Boris Johnson said that all Plan B measures - including mandatory face masks and work-from-home guidance - will be dropped from next week, sparking calls for caution from healthcare leaders and scientists, who also questioned the timing of the announcement amid the political storm engulfing No 10.
However, the ONS data suggests that the worst of the Omicron wave has passed, with government figures also pointing to a drop in daily hospitalisations across much of Britain.
“We are now reaching a stage where a large proportion of people in UK now have some immunity to Covid either because the have been vaccinated or infected,” said Professor Irene Petersen, an epidemiologist at University College London.
“The numbers of cases seems to have peaked and fallen substantially in the last week. The figures we need to watch carefully are the hospital data.”
Professor Francois Balloux, director of the UCL Genetics Institute, said: “The Covid-19 Omicron wave is currently receding in the UK, with number of cases having fallen sharply over recent days, and hospitalisations now following suit. The situation provides a case for lifting restrictions.”
According to the ONS report, one in 20 people in England (3 million) had coronavirus in the seven days to 15 January - down from one in 15 (3.7 million) in the previous week.
In Scotland, around one in 20 is estimated to have had Covid-19 last week, or 236,600 people, down from 297,400. For Northern Ireland, the latest estimate is also one in 20, but the number of people testing positive is up slightly from 99,200 to 104,300, with the ONS describing the trend there as "uncertain".
Meanwhile, in Wales the estimate is one in 25, or 112,100 people, down from 169,100.
Sarah Crofts, head of analytical outputs for the ONS survey, said: "Our latest figures show a welcome decrease in infections across most parts of the UK and among all age groups, apart from younger children.
"We will continue to closely monitor the data to see if this week's decrease carries forward."
The ONS study is a more reliable guide to the level of coronavirus across the country than the number of new cases reported every day by the government.
This is because the number of infections provides a snapshot of the prevalence of Covid-19 within the entire community population of the UK, and estimates the percentage of people who are likely to test positive for the virus at any one point - regardless of when they caught the virus, how long they have had it, and whether they have symptoms.
It is based on a sample of swab tests collected from households across the UK.
There are also 19,450 people in UK hospitals with Covid-19, according to the latest government data. During the second wave of the pandemic, this number peaked at 39,254, on 18 January 2021.
There are signs that, in London, where Omicron first took hold, hospital admissions are falling - another signal the wave has peaked.
Prof Petersen said: “To me it seems as we are at a crossroad. On one side we currently have a relatively high level of immunity due vaccination and recent infection. Yet, there is no guarantee that will be enough to keep the epidemic under control.
“If we went back to pre 2020 activities/interactions tomorrow it is likely that we would see a surge in cases again. However, I doubt that will happen even with the Plan B restrictions lifted.”
Dr Peter English, a former chair of the British Medical Association’s Public Health Medicine Committee, said: “The Omicron wave may now be peaking, but case numbers remain very high. The strong desire to return to normal is understandable, but we should be cautious. Many people are still susceptible to Covid-19 and highly vulnerable.
“Sars-CoV-2 has not gone away. It will continue to mutate, to become more infectious and to evade immunity from previous infection or vaccination. We may see further waves of infection from existing variants as our immunity wanes.”