Hawke's Bay health officials are urging people to turn on the Bluetooth function of their Covid Tracer app ahead of a major concert on Saturday.
About 20,000 people are expected to attend the Six60 gig at the Tomoana Showgrounds in Hastings.
Hawke's Bay medical officer of health, Dr Nick Jones, says the Bluetooth function is vital for big events.
He says it's like the phone giving an anonymous digital handshake to other nearby phones, with the records then stored in the device.
"It's great that everyone is scanning but of course that just tells you that you were there at the concert.
"Only a very small proportion of the people at the concert would have really met that definition of being a close contact so it just helps us to focus in on the people who are really most at risk and for them to get that message early."
Dr Jones says that doesn't mean people should stop scanning the QR codes.
"The QR code is great as well.
"If the vendors, say the food stall vendors at a concert, had QR codes and you scanned that, that would be really helpful because that would limit the numbers [of people to be traced in the event of a case]."
The event kicks off at 5pm with several support acts before Six60 perform.