Mr Shorten told the Seven Network's Sunrise on Tuesday, employees did not have to use their holiday leave, only sick pay, before becoming eligible.
The $750 relief payment will become available from Wednesday, after a change of heart from the government following an emergency National Cabinet meeting at the weekend.
Treasurer Jim Chalmers says the government is "flexible" on a possible extension for the payments, which are due to end in September.
Burnet Institute chief executive Brendan Crabb says as the nation grapples with another winter wave, authorities need to look at interventions to keep case numbers at a steady level.
"We had this model that says it doesn't really matter how much COVID is in the community, we want to protect our elderly and most vulnerable people and keep our hospitals running," Professor Crabb told the ABC.
"That strategy has chosen or proven not to work very well.
"We are going through a rise at the moment that should peak sometime in the next month, it looks like a very worrying high level but they never go low."
Prof Crabb said a reset was needed to help get cases to a lower baseline, involving more vaccines, measures for more clean air, as well as testing and isolation.
He said a collective mentality was also required on renewing strategies or the nation could expect more virus waves.
"We're getting there, we're just a long way behind the eight ball. We have this 'COVID is in the rear-view mirror' mentality," Prof Crabb said.
NSW and Victoria reported almost 26,000 new cases and 51 deaths on Tuesday, with data for other states and territories still to come.
There are more than 340,000 active coronavirus cases Australia-wide, with more than 5100 patients in hospital care.
With case numbers soaring, NSW Premier Dominic Perrottet has raised cutting the isolation period of seven days for people who test positive.
But Prime Minister Anthony Albanese rejected those calls, saying on Monday "now is not the time" for existing requirements to be changed.
LATEST 24-HOUR COVID-19 DATA:
NSW: 13,554 cases, 26 deaths, 2205 in hospital with 60 in ICU
Victoria: 12,201 cases, 25 deaths, 897 in hospital with 34 in ICU
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