The two vaccines will be available at state-run clinics from Monday.
The state will become the first in Australia to make both vaccines an option for those over 16.
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Premier Steven Marshall confirmed the news on social media.
"Vaccination is our pathway out of the pandemic & will help keep our state safe and economy strong," Mr Marshall wrote on Twitter.
It's understood 127,000 booking slots would open from Monday to give younger South Australians the opportunity to get vaccinated.
The appointments will be for September and October, when Pfizer supplies become available.
More details on the announcement are due to be made today.
It comes as South Australia health authorities have defended a decision to enforce a double quarantine period of athletes returning from the Olympics.
Australian athletes currently quarantining in Sydney will have to undertake a second 14-day quarantine period on arrival in Adelaide.
The extra 14 days was imposed after last month after a returned traveller from Argentina contracted COVID-19 in Sydney and sent South Australia into lockdown.