It was optimized by checkerboard titration using recombinant SARS-CoV-2 spike-S1-RBD protein as an antigen.<h4>Results</h4>We found that, compared to the RT-PCR as the standard method, the in-house CovIgM-ELISA displayed sensitivities of 96.15% and 93.22% for samples collected up to 30 or 60 days after infection, respectively, as well as 95.59% specificity with 97.3% accuracy. Here, PSMD1 is linked to infection.