Regarding ELISA kit for the detection of CoVID-19, we could only provide this item: CSB-EL3325HU, Human Novel Coronavirus Nucleoprotein (SARS-CoV-2 N) IgG Antibody ELISA Kit. It is only for research use, not for diagnostic purposes.
Usually, IgM is generated first in the primary immune response. IgM appears first in the process of virus infection, but it doesn't last long; IgG is the main antibody produced by the re-immune response, and it lasts for a long time. Generally, it indicates a past infection.