So i guess without vaccination
Negative COVID Test
You need to show a PCR test no older than 72 hours OR an antigen test no older than 48 hours. (For travellers from certain countries, only PCR tests are valid, please see below.) Tests need to be issued by a medical authority; self-tests are valid for 24 hours only if the result is entered into an official data processing system (except Vienna). Children under 12 do not need to show a test.
or if you are planing to do a day hike in Austria and forgot to do the test prior, you just register online at the border and have 24h to submit the test if you plan to stay in Austria.otherwise no need. I had one hiker that 3G rule was not applicable so we registered him online at Kufstein border. Hope the info helps ;)