The Australian government is in "active discussions" with American pharmaceutical giant Pfizer and other unnamed companies over potential vaccines for COVID-19, the Health Department says.
But little detail has been given about those talks, leading independent Senator Rex Patrick to call for transparency not just on the negotiations, but Australia's entire vaccine strategy.
Department of Health secretary Brendan Murphy told Senate estimates it is still not guaranteed that a successful vaccine for COVID-19 would be found, but that confidence was growing as clinical trials continued.
The government was criticised for being slow to sign the deals, as other countries had already inked deals for multiple candidates.
But Professor Murphy said Australia wouldn't be "stuck in a queue" behind other countries who had signed deals with the company if the vaccine was successful.
The Morrison government has put about $2 billion towards a vaccine, with discussions occurring with a number of companies.
Professor Murphy said those conversations were commercial in confidence, raising the ire of Senator Patrick, who also had a Freedom of Information request for information on the vaccine blocked on national security grounds.
"The federal government's habitual resort to secrecy and obfuscation is absolutely unacceptable," he said.
"It's ridiculous to claim that the vaccine strategy is a national security matter."
Senator Patrick said the lack of information given at Senate estimates about how a vaccine would be distributed and what groups would be prioritised "deepened his concern".
The department said it expected people would need more than one jab of the vaccine candidates currently in trials.
"We're expecting that any vaccine that we know about at this stage would require two doses, so that means we require 50 million for the Australian population," the department's associate secretary Caroline Edwards said.
"Of course that depends on all vaccines being safe and effective.".