Those at the highest risk of contracting monkeypox will receive the first vaccine doses as NSW's rollout begins, in what's been labelled a "breakthrough moment".
NSW Health will from Monday supply 5,500 doses of the JYNNEOS smallpox vaccine to targeted groups deemed most vulnerable if the virus becomes endemic.
More than 30 cases have now been confirmed in NSW, with the majority of those picked up overseas.
In July, Australia's chief medical officer declared the spread of monkeypox a "communicable disease incident of national significance".
Men who have sex with men are considered most at risk of contracting monkeypox, which spreads through skin-to-skin contact.
Gay, bisexual men and men who have sex with men who are homeless, sex workers or have significant drug issues that impair their judgement are among the specific groups to receive the first doses.
Others include those who are HIV positive, immune suppressed or undergoing post-exposure prophylaxis for close contacts.
A small number of people who have booked travel to the US, UK and North America before October 31 are also eligible.
The rollout will expand once another 30,000 doses arrive next month. Authorities have secured 70,000 further vaccines for next year.
NSW Health director of health protection, Jeremy McAnulty, said the virus was spreading quickly in other countries.
"Most people are not at risk from monkeypox," he said. "To be infected you typically need close skin-to-skin contact.
"And those who are most at risk are men who have sex with men.
"We're particularly concerned that men who have sex with men are protected."
Dr McAnulty said the rollout was being staged because of a global scramble to obtain the new-generation vaccine, which is only made by one company.
Health authorities are also urging at-risk people to practice safe sex and limit their sexual partners.
Monkeypox is a disease usually associated with central and west Africa but, since May, there have been outbreaks across the world.
There have been more than 26,000 cases reported internationally, with most identified in the US and Europe.
In Australia, 58 people have been confirmed to be infected, including 33 in NSW.
Only two of those cases are believed to be locally transmitted, and most were infected while overseas.
Symptoms usually develop two weeks after exposure and include headache, fever, chills, sore throat, muscle and body aches, fatigue, rash, and swollen lymph nodes.
The acting chief executive of HIV support and sexually diverse health service ACON, Karen Price, said case numbers in Australia are "extremely likely to increase".
Ms Price says getting vaccines to people who are most at risk is "imperative" for protecting the broader community.
"We acknowledge not everyone in our communities who wants a vaccine will be able to access it initially," she said.
"We are engaged in discussions and would ask people to continue to be patient as NSW Health and community organisations work through vaccine distribution."
NSW Health is working with GPs and doctors who will identify vulnerable patients and offer them the vaccine.
The Royal Australian College of General Practitioners rural chair Michael Clements says the start of vaccine programs across the country was a "breakthrough moment".
"Fortunately, we have not had many cases in Australia and by rolling out this vaccine we can limit community transmission and stop the virus taking hold," he said.
Dr Clements said he did not want patients to fear seeking treatment, saying it was crucial "we do not stigmatise people who contract this virus".
"Please remember that anyone can contract monkeypox and it is not a sexually transmitted disease," he said.
"This is just a virus, and we need to deal with monkeypox without stigma or unhelpful commentary."
