If you were exposed to COVID-19, regardless of your vaccination status: CDC recommends that instead of quarantining, you wear a high-quality mask for 10 days and get tested 5 full days after your last exposure (day 6).
If you have COVID-19: regardless of vaccination status, you should isolate from others for 5 days. If after 5 days you are fever-free for 24 hours without the use of medication and your symptoms are improving, or you never had symptoms, you should test on Day 6. If the test is negative, you may end isolation but should continue masking around others and in public. If the test is positive, you should continue to isolate.
Individuals with moderate illness or severe illness or with a weakened immune system, should isolate through day 10 and consult your doctor before ending isolation.