Former prime minister Kevin Rudd has downplayed his role in securing faster Pfizer shipments for Australia.
"I was simply asked by members of the Australian business community, particularly in the US, to do what I could to try and accelerate the delivery of Pfizer to Australia," he told ABC radio.
"I was just doing my bit, what material effect it had at the end of the day, I don't know and we probably will never know."
Mr Rudd said the business figures told him Pfizer was unimpressed with the federal government's "rude and dismissive" attitude to earlier negotiations.
"This stands in stark contrast, as I was advised, to the approach taken by other heads of government around the world, led by the prime minister of Israel, who spoke to the head of Pfizer some 17 times."
He then held private discussions with Pfizer's global chairman about accelerating Australia's vaccine rollout.
Eight days later, a deal was announced.
Mr Rudd would not reveal the business leaders who approached him but said he would not have intervened if he was not asked.
"I would never picked up the phone to the head of Pfizer unless I'd been approached by senior corporates who had already tried, through their own intermediaries, with Pfizer senior management, to open the door."
Mr Rudd denied leaking a letter about his dealings with Pfizer.
Prime Minister Scott Morrison said he had done all he could to fast-track the vaccine supply, including having a meeting with Pfizer when he was in Paris.
"They were all very aware of what we were putting forward," he told 2GB radio.
"The proof of these things is in the eating - when we sought the bring-forward that is what has happened."
Pfizer has rejected suggestions any third party played a role in its contractual negotiations with the Australian government.
John LaMattina, a former president of research and development at Pfizer, said he was surprised by Australia's approach.
Mr LaMattina said Australia had shown a lack of aggression compared to countries like Israel.
"The surprising thing to me was in the initial meetings about a year ago, Australia declined an opportunity to put a contract in for the Pfizer COVID-19 vaccine, they decided to take a wait and see attitude," he said.
"Where the wheels really fell off was later in the year when it was clear that Moderna and Pfizer had gangbuster COVID vaccines.
"Even at that point, Australia only decided to order 10 million doses, which I thought was really a mistake."