To find out an individual's immunity against hepatitis B, we use standard serologic testing [1]. With COVID-19, the FDA[2] and CDC[3] state that you "should not interpret the results of your SARS-CoV-2 antibody test as an indication of a specific level of immunity or protection from SARS-CoV-2 infection".
Which methods can be used to evaluate a person’s level of immunity or protection from COVID-19? How do I know if my 2nd (or 3rd) dose worked? Are there any ongoing trials (for immunity tests)?
[1] https://www.cdc.gov/hepatitis/hbv/pdfs/serologicchartv8.pdf
[2] https://www.fda.gov/medical-devices/safety-communications/antibody-testing-not-currently-recommended-assess-immunity-after-covid-19-vaccination-fda-safety
[3] https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fvaccines%2Fcovid-19%2Finfo-by-product%2Fclinical-considerations.html