England recorded its highest ever Covid-19 infection prevalence in March and cases were still increasing in the over 55s at the end of the month, an Imperial College London survey said, adding that Omicron subvariant BA.2 was now dominant.

Prime Minister Boris Johnson has lifted all Covid-19 restrictions in England, citing the experience with a wave of Omicron infections over new year which saw record cases, but did not produce an equivalent wave of deaths in Britain's highly vaccinated population, Reuters reports.

Imperial's study showed that the peak in infections in March surpassed the highs of the BA.1 Omicron wave in January, reinforcing findings by the Office for National Statistics (ONS) that cases have hit an all time high.

“We don't yet know when we'll see a peak in the oldest age group, the 55+, and because those people are at higher risk of severe outcomes, that is a particular worry,” Imperial epidemiologist Christl Donnelly told reporters.