England’s third national Covid-19 lockdown is helping to reduce infections, a study found, but the prevalence of cases remains high as Prime Minister Boris Johnson eyes a cautious route to re-opening the economy.

The study, known as REACT-1 and led by researchers at Imperial College London, found that national prevalence was two thirds lower between Feb 4 and 13 than it had been in the previous survey that covered Jan 6-22, Reuters reported.

“It’s really encouraging news. We do think that lockdown is having an effect. We’ve seen this quite rapid decline now between January and this month,” Paul Elliott, director of the programme at Imperial, told reporters.

“But [...] the actual prevalence is still very high. We’re only back where we were in September.”