Pfizer has downplayed the role former prime minister Kevin Rudd played in fast-tracking shipments of vaccines to Australia.
The pharmaceutical giant said it was inaccurate to suggest any individual or third party had any role in the contractual agreements.
"The only two parties involved in these agreements are Pfizer and the Australian government," a company spokeswoman told AAP on Monday.
"All agreements and supply arrangements including dose planning are exclusively made with the federal government, and details of the agreement and discussions are confidential.
"All discussions on supply and procurement with the federal government are led by Pfizer representatives in Australia."
Mr Rudd contacted Pfizer at the insistence of senior Australian business leaders based in the United States.
They were concerned Prime Minister Scott Morrison was not pushing hard enough and may have offended Pfizer by sending junior public servants into negotiations.
Mr Rudd met virtually with the global head of Pfizer on June 30 and asked whether the delivery of Australia's doses could be brought forward.
The pharmaceutical boss agreed to investigate what could be done.
Mr Rudd then wrote Mr Morrison a letter to brief him on the discussions, with a deal announced eight days later.
Pfizer has committed to delivering more doses to Australia sooner than expected, with one million doses to be rolled out each week from mid-July.
Health Minister Greg Hunt said he chuckled when he read reports of Mr Rudd's involvement in the outcome.
"We received a letter from the individual in question ... and we said to ourselves, 'Well, no doubt that will be released when our current negotiations are announced publicly'. That is exactly what happened," he said.
Defence Minister Peter Dutton ripped into Mr Rudd over his approach to Pfizer executives and the media reports that ensued.
"I suspect it wouldn't take our greatest detective within the Queensland Police Service to identify who leaked that self-serving letter," Mr Dutton told 4BC radio.
"Kevin claims credit for many things, it used to drive his Labor colleagues crazy."
The defence minister suggested Mr Rudd was inserting himself into the public debate because he was "bored to death in retirement".
The former prime minister said his letter was consistent with Pfizer's public statements.
"Mr Rudd has not claimed responsibility for decisions by Pfizer and - as he made clear to Mr Morrison - all negotiating powers rested with the federal government," a spokesperson said.
"Mr Rudd would definitely not seek to associate himself with the Australian government's comprehensively botched vaccine procurement program."