“Quarantine” means that if you are exposed but healthy, you must stay home (or outdoors well away from others). 

“Isolation” means that if you are sick with COVID-19, you must also try to stay away from uninfected household members as well.

On August 11, 2022, the CDC announced new recommendations for isolation and quarantine.

https://www.cdc.gov/coronavirus/2019-ncov/your-health/isolation.html

Generally, people with COVID-19 disease must isolate for 5 days (and longer if you are sicker or not recovering.  Then, for the following 5 days, they are .expected to wear a mask and avoid unnecessary contact.

People exposed (but not yet sick) are no longer required to quarantine, but they are expected to wear a mask and avoid unnecessary contact for 10 days after exposure.

The recommendations are the same for everyone, regardless of age, and regardless of COVID-19 vaccination status.

Repeat testing after infection is still generally not recommended.  The CDC specifically recommends against repeat testing as a condition of returning to work or school, unless recommended by a physician.  PCR tests can often remain positive long after you are no longer contagious; so return to work or school would be delayed unnecessarily.

     --  Dr. Epstein