Covid infections among five to 11-year-olds are three times more prevalent than in the general population, a Government-backed study has found.
An estimated 4.47% of primary school-aged children have the virus in contrast with 1.41% across the country overall, according to the research.
REACT-1, a joint study by Imperial College London and Ipsos Mori, analysed data from 97,000 volunteers in England to examine national Covid-19 levels between November 23 and December 14.
It predicted the rapidly spreading Omicron variant will become the dominant strain across the country more than three times faster than Delta overtook Alpha.
But the speed of the vaccine rollout to secondary school-aged children and the booster rollout among adults may have helped to curb infection rates among other age groups, researchers said.
The prevalence of Covid-19 in secondary school-aged children, previously the worst-affected age group, more than halved, while among those aged 75 and over it dropped by approximately two-thirds.
Scientists added the figures were taken from a time period when Omicron was only just starting to take hold.
Professor Paul Elliott, who led the study, said the findings showed the R value – the average number of secondary cases produced by one infected person – began shooting up at the start of December.
Viral sequencing data up to December 11 showed that 11 out of 650 cases were the Omicron variant and the rest were Delta.
“From December the proportion of samples which are Omicron has been rapidly increasing, reflecting both the replacement of Delta by Omicron but also the rapid rise in Omicron,” Prof Elliott said.
The study showed the spread is most rapid in London, where the R value started at an estimated 1.41 overall but rose later in December to 1.62.
Prof Elliott said the odds of an infection being Omicron instead of Delta were estimated to increase at a rate of 66% a day – 3.5 times faster than the rate at which Delta outcompeted the Alpha variant.
It comes after the Pfizer/BioNTech coronavirus vaccine was approved for use in vulnerable primary school children.
The Joint Committee on Vaccination and Immunisation (JCVI) updated its advice after the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) found the jab was safe for five to 11-year-olds following a robust review.
In response to the Omicron variant, the committee has also advised that some older children be offered a booster dose.
A low-dose version of the vaccine has been approved for those aged five to 11 who are in a clinical risk group, or who are a household contact of someone of any age who is immunosuppressed. They should be offered a primary course of vaccination – typically two doses.
Prof Elliott added: “The results reported in this round of REACT show that Omicron is spreading rapidly in England and especially in London, which now has the highest prevalence of Covid in the country.
“Compared to the Delta variant, the proportion of Omicron cases is increasingly rapidly.
“The positive news is that both the teenage vaccination and booster programmes have already shown encouraging results, with prevalence amongst 12 to 17-year-olds and those aged 65 and above dropping significantly since the beginning of November.”
Health Secretary Sajid Javid said: “The latest REACT-1 data is yet more evidence that boosters are vital in protecting us from the Omicron variant.
“While infections may be rising rapidly across the country, you can protect yourself, your friends, family and community by getting boosted now – like 28 million others across the UK so far.”