The RTPCR will only work for those with viral RNA in them. So those with active infections. The antibody test won't work until the host produces antibodies agai

The RTPCR will only work for those with viral RNA in them. So those with active infections. The antibody test won't work until the host produces antibodies against the virus (except for false positives). So yeah, the antibody test will detect those who are immune, or at least have antibodies against Covid-19 whereas the RT-PCR will not.