If they are up to date on vaccines
If they have taken the full series of a COVID-19 vaccine and boosters as recommended, they are up to date.
The close contact does not need to quarantine.
The close contact should get tested at least 5 days after close contact. Watch for symptoms and wear a well-fitting mask while around other people for 10 days from the date of last close contact.
Regardless of vaccination status, if a close contact develops symptoms, they should isolate and get tested immediately.
If they test positive, continue to isolate.