Both Josh Lewsey (hamstring) and Iain Balshaw (ankle) were unable to take part in England's 28-17 win over Wales on Sunday because of injury, with Dan Luger moving into the starting XV and Stuart Abbott sitting on the bench.
"Austin Healey is being flown out to Sydney this [Sunday] evening as a precaution as we have injuries to Josh Lewsey and Iain Balshaw," said coach Clive Woodward.
"I must stress that he is not joining the squad, which would be subject to Rugby World Cup approval, and we will continue to monitor the fitness of Josh and Iain over the next 24 hours."
Healey – one of the surprise omissions from Woodward's original 30-man squad – will now travel to Australia after having helped his club Leicester end their worst-ever run of losses on Saturday, beating Zurich Premiership champions Wasps 32-22.
He is the third England 'replacement' to have been called to Australia so far.
Healey would have flown in after England's opener against Georgia -when both Matt Dawson and Kyran Bracken experienced injury scares, but he had a thigh strain and the 'honour' went to Bath scrum-half Martyn Wood.
Wood duly flow out as a precautionary measure, but both scrum-halves recovered and the Bath man was dispatched back to London two days later without even meeting the squad.
London Wasps second rower Simon Shaw was much luckier. The lock arrived in Australia last week after Danny Grewcock had to pull out of the tournament with a broken bone in his hand, and went straight onto the bench for last week's Uruguay game.
Healey's fate should be known later this week when there is more clarity over Lewsey and Balshaw.