Having antibodies does not mean immunity!
Antibodies can be found in the blood if you have and/or had an infection.
IgM Antibody – present if you have an active infection or recently recovered from an infection.
IgG Antibody – present if the infection has passed, but you had the infection.
Having antibodies does not prevent reinfection, but “may” offer some protection (research is needed to confirm this with COVID-19).
One known condition that illustrates this antibody concept is herpes. If you have an active infection and/or have come in contact with the virus in the past, you will have antibodies; however, herpes infections recur thoughout ones lifetime. The antibodies do not prevent the virus from coming back.