The premier, the state's police commissioner and health officials leading the charge against COVID-19 have been among the first to get the coronavirus vaccine in South Australia.
SA has received 4000 doses, with 3000 to be distributed from the Royal Adelaide Hospital and 1000 from the Flinders Medical Centre.
The state's 1700 frontline workers will be targeted first, including 500 staff at Adelaide Airport, more than 1000 people who work in Adelaide's quarantine hotels and 50 people involved in transferring arrivals.
At the Flinders Medical Centre, staff working in the emergency department, the respiratory ward, the intensive critical care unit and the COVID-19 testing clinic will be prioritised.
From there, SA will vaccinate people considered at most risk of getting the disease and at most risk of severe complications if they become infected with another 8000 doses to arrive during the next three weeks.
Chief Public Health Officer Nicola Spurrier said she was "so excited" that the vaccination program was underway.
"It's been a gruelling 12 months for so many of us," she said on Monday.
"People have lost their jobs, we've had business impacted and the border closures have had such a profound effect on so many South Australians.
"With this vaccine, it's the next step in being able to prevent this pandemic and the effects that it has had on our society."
Professor Spurrier said she had full confidence in the safety of the Pfizer jab and urged as many people as possible to take part.
She said the side effects were similar to those often experienced by people who received the annual influenza vaccine.
"You might have a bit of a temperature, you might feel a little bit under the weather," she said.
"But actually that's your body reacting to the vaccine and developing an immune response."
However, she said people who had previously had a severe reaction to a vaccine should consult a doctor to discuss their particular circumstances.
A special adverse reaction clinic has also been established at the RAH.
Among the first frontline workers to take part on Monday was nurse Annabel Thomas, who has worked in Adelaide's quarantine hotels and who also spent time in Victoria during Melbourne's second wave of infections last year.
"I can't stress enough to all South Australians that vaccination is a vital part of getting back to life pre-COVID," she said.
"I'd strongly suggest everyone be a part of this program."
Premier Steven Marshall said while all people were urged to get the free vaccine, it would remain voluntary.
He said the rollout would be vital in keeping South Australians safe and the economy strong.
"We are about to embark on the state's biggest-ever peacetime operation," he said.
SA reported no new coronavirus cases on Monday and has just three active infections, all returned travellers in hotel quarantine.
Officials have also indicated the state is poised to lift its remaining travel restrictions with Melbourne.
Under the existing arrangements, people coming from the Greater Melbourne area are not permitted to enter SA.
Exemptions are provided to returning local residents, people relocating permanently and essential travellers.
Police Commissioner Grant Stevens said a meeting of the state's transition committee on Tuesday would discuss easing the measures from Thursday.