Specialists say the group is significantly over-represented in hepatitis B cases.
It is prevented with a simple three-dose course of injections.
But while Indigenous adults are one of the groups most at risk of being infected with hepatitis B, many are not protected.
A new Australian report for the World Health Organisation calls for free hepatitis B immunisations for all Indigenous adults.
Royal Melbourne Hospital infectious-diseases specialist Benjamin Cowie is one of the authors.
"An Aboriginal person has four times the risk of getting a new or incident acute hepatitis B, compared to a non-Indigenous person. So, using that as the foundation, we then went on and examined the potential impact of a vaccination program targeting susceptible Aboriginal and Torres Strait Islander adults to protect them against acute or incident hepatitis B."
Hepatitis B is spread through bodily fluids and can lead to chronic liver disease or cancer if left untreated.
Dr Cowie says the researchers found one case of hepatitis B would be prevented for every 150 Indigenous Australians vaccinated.
"That's a very low number needed to vaccinate, compared with many of the other existing vaccination programs which are supported by the Australian government. So by vaccinating just a proportion of those who remain susceptible amongst the Aboriginal and Torres Strait Islander adult population, hundreds of hepatitis B infections would be prevented in the next 10 years."
All Australian babies are offered free hepatitis B immunisations under the National Immunisation Program.
The vaccines for adults would be free, but not compulsory.
The report's lead author, Kristine Macartney, from the National Centre for Immunisation Research and Surveillance, says the current system for adults is inequitable.
She says free vaccinations for them are only available in some states.
"When the vaccine's not free and it's not promoted, that it can't be just pulled out of the GP's or the clinic's fridge, we don't see high uptake of vaccine in that context. And this is about saying, if we went the extra mile* and we were able to provide the vaccine free at the time of seeing a patient, and at the time of ordering their test for hepatitis B, we could then really improve coverage. We're not suggesting that everybody could be vaccinated. But even if we're looking at half the people who remain susceptible being vaccinated, we'll see some good impacts."
A community worker with the support group Hepatitis Victoria, Sione Crawford, works closely with Aboriginal adults at risk of contracting hepatitis B.
He says the absence of a national program is a glaring oversight.
"We need to ensure that Aboriginal people know that their health is valued and that we are completely willing and able to invest in that for the future. We know that the disparity between Aboriginal health and non-Indigenous health in Australia is wide, and we need to close that gap. This is one really quite simple way to do that."
A spokesman for federal health minister Sussan Ley says the focus on immunising children is considered the primary approach to immunisation.
He says independent experts regularly look at new evidence, such as the World Health Organisation paper, to assess whether immunisation is indicated and cost-effective.
The global journal of that organisation will publish the Australian report next week.
