South Australians at the highest risk of contracting monkeypox will be given the first vaccine doses that have arrived in the state.
Yesterday, the state received 900 doses from the national stockpile following rollouts in New South Wales and Victoria.
More vaccines will be allocated to South Australians in the coming months.
Chief Public Health Officer Nicola Spurrier said two doses of the vaccine will be required for each person and 900 vaccines was just the "initiative allocation".
"In first instances we will be holding doses back in case we have close contacts of cases," she said.
"We can use it before someone's exposed or after their exposed, particularly if it's four days after the exposure."
Professor Spurrier said men who have sex with men who were living with HIV or had a recent sexual infection, or people receiving preventative medication for HIV, would be eligible for the first batch of monkeypox vaccines.
"Those particularly groups are known to health clinics, so the way we are doing this in South Australia is going to those people we know are at higher risk and we will be saying to them they're eligible for vaccine,"" she said.
South Australian recorded its first case of monkeypox in a man returning from overseas in June.
Professor Spurrier said SA Health sexual health clinics were open for testing and pathology collection for monkeypox.
"This is not just a sexually transmitted infection," she said.
"There is going to be at some point other people exposed, whether that's a health worker or family member, because it can be transmitted from respiratory droplets and also from the lesions."
The "third generation" vaccine from Barvarian Nordic is new, but there are no known serious side effects, Professor Spurrier said.
"One of the things that is important is making sure if you have symptoms to be diagnosed very quickly, but one of the important things is having a vaccine," she said.
Symptoms of monkeypox to watch out for, particularly for people returning from overseas, include fever, headache, fatigue, rash, lesions and soreness in the genitalia area.
