COVID-19 infections have fallen by 30% during England’s month-long national lockdown and the virus is now in retreat, a large-scale study of more than 100,000 volunteers showed on Monday.

England began its second national lockdown on Nov. 5 to curb rapidly rising infections and protect its health system. The country is due to return to a regional approach to restrictions from Dec. 2.

Levels of infection fell 30%, with 96 people per 10,000 infected between Nov. 13 and Nov. 24, according to interim results of the study by Imperial College London and Ipsos MORI.

The last iteration of the research, carried out between Oct. 16 and Nov. 2, showed 130 infections per 10,000 people.

“The findings show cases were rising as the country entered lockdown, but this was followed by a decrease as national measures successfully lowered infection rates across the country,” a statement issued by the health department said.

Prime Minister Boris Johnson faced criticism over the decision to lock down from within his own party where some said it was an unnecessary infringement on civil liberties. The opposition Labour Party said he had been too slow to react.

The reproductive number of the virus was estimated at 0.88, reinforcing data released on Friday which showed infection numbers were shrinking by between 0% and 2% every day.

While the statement said the prevalence of the disease was still high, it showed a sharp decrease in several areas of northern England which are due to enter the toughest tier of restrictions next week.

That could fuel further unrest within Johnson’s Conservative Party, where many lawmakers are unhappy at a system which places more than a third of the population under far-reaching restrictions on daily life.

Those measures are due to be put to a vote on Tuesday, in which Johnson may face the political embarrassment of having to rely on opposition party votes to pass the new rules.