There's no simple answer. It really depends on severity of symptoms, length of the disease course, and immune system response. Some patients never produce detectible levels of antibodies, in others they may persist for years.

Patients who receive a negative antibody test after a suspected COVID-19 case might want to get a T cell test since that is another way to confirm previous infection.

https://www.fda.gov/news-events/press-announcements/coronavi...