Prime Minister Scott Morrison has moved to assure Australians any coronavirus vaccine will not be compulsory, despite earlier saying he expected that would be the case.

On Wednesday, the federal government announced it had signed a letter of intent with British drug company AstraZeneca, in a step towards securing supply of a leading vaccine candidate that could be supplied free to Australians.

If a successful candidate is discovered, the government wants to see 95 per cent of Australians vaccinated.

Talking up hopes of a successful vaccine on Wednesday morning, Mr Morrison told Melbourne radio station 3AW he would “expect it to be as mandatory as you can possibly make it”, noting the devastation COVID-19 has wreaked on the world.

“There are always exemptions for any vaccine on medical grounds, but that should be the only basis,” he said.

But just hours later, Mr Morrison told listeners on Sydney radio station 2GB that the government would not make vaccination mandatory for anybody.

“It’s not going to be compulsory to have the vaccine,” he said.

“There are no mechanisms for compulsory … I mean, we can’t hold someone down and make them take it.”

While the government does not mandate vaccination for other diseases, parents can lose access to government payments like the Family Tax Benefit A and the Child Care Subsidy if their children do not meet immunisation requirements.

Mr Morrison said the government would take measures to “encourage” people to be vaccinated.

Scott Morrison backed away from suggesting a COVID vaccine would be mandatory for Australians.

PM walks back mandatory vaccination comments

“Nobody’s going to force anybody to do anything as a compulsory measure, but we will certainly be encouraging people to take this up,” he said.

“There will be a lot of encouragement and measures to get [a] high rate of acceptance.

“What we want to achieve is as much vaccination as we possibly can, should the vaccine actually prove successful.”

It is understood the government hopes to have a more formal agreement with AstraZeneca in place within coming days, once a local manufacturer is locked down.

Australian biotech giant CSL is the frontrunner for local production of the vaccine.

AstraZeneca Australia’s Liz Chatwin acknowledged Australian scientists had never made the particular type of vaccine before.

“This is an adenovirus vector vaccine, so it hasn’t ever been produced in Australia,” she said.

“This is a massive scale-up activity. We haven’t done it before.”

Sources say securing a contract with AstraZeneca is one thing, but manufacturing it is another.

The time and effort required for a company like CSL to “scale up” and produce a new type of vaccine for 25 million people is “enormous”, according to industry insiders, and will likely be the cause of any delays.

Labor criticised the agreement with AstraZeneca as too small a step and lacking in detail.

“These comments from Scott Morrison are further proof that the Government is making it up as they go along when it comes to the vaccine,” health spokesman Chris Bowen said.

“Of course we need a strategy to maximise the uptake of the vaccine amongst Australians – but it doesn’t appear that the government has done any thinking on how they are going to roll out the vaccine, let alone how they are going to secure Australia supply of the vaccine.”

-ABC