In a week-long operation, police used plain clothes officers to monitor people checking in at various venues including retail outlets, cafes and restaurants.

It resulted in a daily increase in the number of check-ins of between 500,000 and 600,000 to a high of 1.78 million on May 15.

Police also issued 563 cautions and one expiation notice to individuals and 83 cautions to businesses.

Operation Trace was prompted by a dramatic fall in the use of QR codes in recent weeks, largely attributed to complacency with no local cases of coronavirus for some months.

"We have been tolerant but people need to start using the system if we are to continue seeing an increase in public activities across the state," Commissioner Grant Stevens said when the operation was launched.

However, after a meeting of the state's transition committee on Tuesday, Mr Stevens said he was pleased with the public's response to the blitz.

"We are seeing significant levels of increased compliance and I'm sure everybody out and about in the community will be noticing more people coding in," he said.

"I'm very pleased with the way the community has responded to this alert we've put out."

QR codes allow health officials to quickly trace people who may have come into contact with COVID-19.

The information is only kept for 28 days and is only available to SA Health's contact tracing team.

The codes are mandatory in almost all venues across SA.

Australian Associated Press