The overall Covid prevalence rate more than doubled last month from February when infection rates were falling from the Omicron-led January peak, the React-1 study led by Imperial College London found. Since then, the emergence of BA.2 – a more-transmissible version of Omicron – has accelerated new infections and become the dominant strain in England, accounting for about 90 per cent of the samples that tested positive.

The higher infection rates may result in an increase in hospitalisations despite the higher levels of vaccination among the population, said Paul Elliott, director of the React programme, and chair in Epidemiology and Public Health Medicine, Imperial College London.

Rates of Covid-19 are growing among adults over 55 years driven by higher mobility and waning immunity given that they received their booster shots earlier compared to other age groups, the study said.

The latest results are the 19th round of the React-1 study and will be the last as the programme comes to an end at the same time the UK cuts back on free coronavirus tests.

The Imperial College researchers raised concerns that it will become more difficult to detect emerging variants as the government scales back testing.

“There are a lot of variants out there and it’s looking at the patterns that helps to identify variants of concerns and make sure that people see what’s coming,” said Christl Donnelly, a professor of statistical epidemiology at Imperial.