Despite the possibility of reduced immune response in people who are immunocompromised, antibody testing to assess for immunity following COVID-19 vaccination is not recommended. The reason is that, while the presence of antibodies in the blood can be an indicator of either previous infection or vaccination, the WHO states that there is no confirmed evidence that people who have antibodies are protected from a second infection. Furthermore, many antibody tests for COVID-19 do not quantify the amount of antibodies but only indicate if they are detectable, and even if a semi-quantitative test is performed, results from such a test should not be interpreted as an indication of the degree of immunity or protection from reinfection, according to the FDA