LONDON : COVID-19 infections in England have quadrupled in a month since early June, a large prevalence study showed on Thursday, ahead of Prime Minister Boris Johnson's plan to fully re-open the economy in two weeks' time.

Johnson said he aimed to end most legal coronavirus restrictions on July 19, even though models suggested cases would rise, saying that he was reconciled to more deaths from COVID-19 but that life needed to return to normal.

According to the research, led by Imperial College London, cases were estimated to be doubling every six days as a new wave fuelled by the Delta coronavirus variant picks up pace.

The study, one of Britain's largest with 47,000 people returning tests from June 24 to July 5, found national prevalence was 0.59%, or 1 in 170 people, compared with 0.15% in the last round between late May and early June.

"It's very difficult to make an argument, based on the type of data that we get, that it's a good thing to open early," Steven Riley, Professor of Infectious Disease Dynamics at Imperial College London, told reporters.

He added that the government had to take other, non-epidemiological factors into account when making its decision.

The research found that COVID infection rates were three times lower in people under 65 who had received two doses of vaccine compared with those who were unvaccinated, showing the importance of the vaccine rollout in reducing case numbers. (Graphic on global vaccinations) https://tmsnrt.rs/3tUM8ta

There was no direct evidence that the men's Euro 2020 soccer championships had fuelled the rise in cases, Riley said, but women were 30% less likely to test positive than men, most likely due to different social mixing patterns.

"The degree to which men and women are socialising is likely to be responsible," Riley said, adding that specific concerns about London's Wembley Stadium hosting games might not be as important as an increase in indoor mixing around the nation.

"It could be that watching football is resulting in men having more social activity than usual."