source: Can an antibody test tell me if my vaccine worked?
Unfortunately, there’s no similar test for SARS-CoV-2. In fact, the FDA warns against trying to check for vaccine-induced immunity using currently available antibody tests. For one thing, many tests only detect antibodies to the nucleocapsid protein, which are found only in people who have survived a natural infection. If you’ve never had COVID-19 and take one of those tests, you’ll get a negative result.
Unfortunately, there’s no similar test for SARS-CoV-2. In fact, the FDA warns against trying to check for vaccine-induced immunity using currently available antibody tests. For one thing, many tests only detect antibodies to the nucleocapsid protein, which are found only in people who have survived a natural infection. If you’ve never had COVID-19 and take one of those tests, you’ll get a negative result.