The roll out of a vaccine for the virus by the end of 2021 underpins both the economic and health arms of this week's budget, but experts say it's a gamble.

"You're betting on a product that doesn't exist yet, and apart from that there isn't a whole lot for public health," said chief executive of the Public Health Association of Australia Terry Slevin.

Spending by the Australian government on reacting to the pandemic has topped $16 billion, on things such as personal protective equipment, telehealth, treatments and extra hospital funding. A deal has also been signed for the supply and manufacture of two promising vaccine candidates, at a cost of $1.8 billion.

But experts also say we must also prepare for COVID-19 to be around long-term.

"My concern is it doesn't have a plan for between now and the vaccine, or the alternative path we might end up taking in the absence of a vaccine," Professor Catherine Bennett, Chair of Epidemiology at Deakin University said.

Public health investment is not as simple as ensuring the national medical stockpile is replenished, they say, but investing in a skilled workforce.

"The world has just gone through a public health emergency in this pandemic but the budget did not prepare Australia for the rest of this pandemic and for pandemics in the future," Professor Slevin said.

"The capacity to respond to future pandemics has to be reliant on the public health workforce having the capacity to fight off future disease."

"That investment opportunity has been missed," Professor Slevin said.

Investment in more public health professionals and in preventative health measures would not only benefit Australia in the event of a pandemic, but in the battle against chronic disease, he said.

Workforce capacity takes years to build, and the outbreak in Victoria showed what could happen without enough public health professionals.

"The truth is no jurisdiction would have had the necessary capacity to deal with the size of the emergency that the Victorians had to deal with, but many jurisdictions worked very hard to hold the line."

Treasurer Josh Frydenberg wouldn't say on Wednesday whether the Australian Health Protection Principal Committee had endorsed basing the budget on the assumption that the majority of the population would be vaccinated against COVID-19 by the end of next year.

"It was worked out by Treasury in conjunction with the Health Department, and they worked through the various scenarios," he said.

"These are very uncertain times and as a government we have taken every step possible to give Australia the best chance of getting a vaccine."

Professor Bennett was surprised the committee wasn't part of the conversation about basing so much of the budget on the availability of a vaccine.

"It would be good to see us thinking beyond COVID as well, about measures that will help support and prevention, to really take the lesson from this about what we need to do to be in a better state of pandemic preparedness altogether."

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In the lead up to the budget on Tuesday, Labor promised that if it were to win government it would introduce a Centre for Disease Control, that would coordinate Australia's response to pandemics, house experts to monitor threats and run exercises to test preparedness.

Professor Bennett said the idea had merit, particularly due to the nature of Australia's health system, with funding and responsibilities spread across federal and state and territory governments.

Exercises planning for pandemics could have helped authorities to prepare for situations like that faced by the aged care sector, or that the health workforce would be faced with mass furloughs of staff due to COVID-19 exposure, she said.

The Department of Health responded to the criticism by saying the government was spending $115.5 billion on health in 2020-21 and $467 over the forward estimates on health services.

"The 2020-21 Budget funds the government's ongoing health response under the Australian Health Sector Emergency Response Plan, extending initial key COVID-19 health initiatives," a spokeswoman said.

"It helps chart the road out, including through unprecedented mental health support, and implementation of our COVID-19 Vaccine and Treatment Strategy."