How long IgM and IgG antibodies remain detectable following infection is not known.
...
it remains uncertain to what degree and for how long individuals with antibodies (neutralizing or total) are protected against reinfection with SARS-CoV-2 or what concentration of antibodies may be needed to provide such protection.
> "Having antibodies does not guarantee immunity."
Sure, but it seems to have worked so far. And if having natural antibodies doesn't give long-term immunity, then will vaccine-induced antibodies? We don't know.
> "How long IgM and IgG antibodies remain detectable following infection is not known."
Having detectable antibodies is not the same thing as immunity.