The current wave of Covid infections may now have peaked in younger people, a study has found, but record high levels of the virus in the community are contributing to 12-hour waits at some A&E departments.

       In its latest and last edition, Imperial College London's React study – which has been analysing Covid prevalence in the community throughout the pandemic – found that 6.37 per cent of people in England had the virus, up from 2.88 per cent in a month and a new record high.

       However, there were signs that, towards the end of the testing window between March 8 and 31, case rates in younger sections of the population were dropping.

       "We are reassured rates in younger groups seem to be coming down – they can't go up forever," said Prof Paul Elliott, the chairman in epidemiology at Imperial College London and React director.

       Rates also seem to be flattening in adults aged between 18 and 54, data show.

       But prevalence in older people is still increasing, which is likely to cause an increase in the number of hospitalisations and deaths in coming weeks as this is the most vulnerable section of the population.

       Dame Jenny Harries, the chief executive of the UK Health Security Agency (UKHSA), said: "These latest study results are another reminder that the pandemic is not over, and there is still a real risk to many of us of catching Covid with infection rates so high."

       Prof Elliott said: "These trends are concerning, since when a very high number of people are infected this may lead to more people becoming seriously ill and needing to go to hospital."

       With Covid in the community at unprecedented levels, pressure on health services is again beginning to mount.

       Officials from six hospitals on Wednesday issued a joint warning to people to stay away from A&E except in "genuine, life-threatening situations" after some patients had to wait for more than 12 hours.

       Hospital trusts across West Yorkshire and Harrogate in North Yorkshire – an area covering more than 2.5 million people – said pressures had left them with no choice but to prioritise patients presenting with acute illness or injuries.

       West Yorkshire Association of Acute Trusts said its most recent emergency department figures showed a 14.2 per cent increase in attendance compared with the same week last year.

       The Imperial researchers sequenced more than 3,000 swabs and found that 90 per cent were the BA.2 version of the omicron variant that is causing the current wave.

       The study also found five cases of a recombinant, a variant formed when the BA.1 and BA.2 variants infected the same person and merged.

       More than 600 cases of this variant, described as omicron XE and thought to be 10 per cent more transmissible than BA.2, have been reported by the UKHSA.