You will be required to quarantine for 5 days if you have had contact with anybody who has tested positive for COVID-19, even if you are vaccinated or if you test negative.
The only time you will not be expected to quarantine after being in contact with someone is if you are within 90-days from the end of the self-isolation period and can prove this by use of an EU Green Certificate or another official recognised document.
Contact is considered anyone who you spent more than 15 minutes without a mask within 2 meters.