I am sure you are aware that recommendations from WHO, CDC, etc ... is to not change risk assessment after a positive test to antibodies as the level, strength, duration of immunity provided is unknown and only thesis are there so far. They clearly emphasis to follow the same barrier measure as before the test. The number of recorded re-infections is now close to 900 for 5 countries only.
https://www.who.int/news-room/q-a-de...id-19-serology
https://www.cdc.gov/coronavirus/2019...-overview.html
https://www.sciencemag.org/news/2020...s-quickly-some