Covid-19 cases dropped by 21% compared with slotxo other areas during a mass testing pilot in Liverpool, research has shown.
People living or working in the city were offered tests whether or not they had symptoms from November to April.
More than 3,200 staff days among key workers were saved from being lost to quarantine through a test-to-release scheme, scientists said.
University of Liverpool's Prof Calum Semple said the pilot was "incredibly valuable" for future scenarios.
Liverpool had one of the highest infection rates in England when the city-wide testing scheme began in November.
The study, by the University of Liverpool and the Department for Health and Social Care, found that in six months, 283,338 people in the city took a lateral flow test.
The research revealed there was an 18% increase in case detection up to mid-December compared to other areas.
About 6,300 individuals who declared no symptoms tested positive, and researchers also suggested between 850 and 6,600 infections were prevented by the pilot.
The speed at which lateral flow results were available, compared to PCR tests which are analysed in labs, saved about a day in the time it takes to identify someone as likely to pass on the virus, scientists said.