Foxhall Internists now has two different antibody tests to look for antibodies against SARS CoV2, the virus that causes COVID-19. One test looks for antibodies against the spike protein, which turn positive either after natural infection or vaccination. The other test looks for antibodies against the nucleocapsid of the virus, which only turn positive after natural infection (and not vaccination).
Common questions include:

  • Can these tests determine whether I have been previously infected (even after vaccination)? Yes. While not with 100% certainty, testing for both sets of antibodies can help distinguish whether you have antibodies from natural infection (antibodies to the nucleocapsid) as well as from vaccination (antibodies to the spike protein).

  • If I want to see how my body reacted to the vaccine, when should I test? While there is no official cut-off date, many experts recommend waiting approximately 28 days after your final dose to give your body a chance to mount a robust antibody response.

  • Can these antibody tests tell me how much immunity I have to SARS CoV2? No. There is no definitive correlation between antibody levels and immunity. We also cannot distinguish between immunity to the original circulating virus or the new variants. While there is some likely association between higher antibody levels and increased protection, this has not been proven. Furthermore, there are a number of patients without measurable antibodies who have a cellular (T-cell) immune response from prior infection and/or vaccination, and therefore some level of protection.