Although specific IgG Abs to SARS-CoV may have significantly waned in many recovered patients from the 2003 epidemic, and likely could not be sufficient in protecting individuals from SARS-CoV-2 infection, there is still evidence that SARS-CoV vaccines and NAbs could serve in treatment for COVID-19. For this reason, it is crucial to detect Abs titers for convalescent COVID-19 patients.