On June 17, the EEOC updated its COVID-19 Guidance to clarify that unlike COVID-19 testing, an anti-body test would be a prohibited medical examination.  The FAQ states as follows:

Question: The CDC said in its Interim Guidelines that antibody test results “should not be used to make decisions about returning persons to the workplace.” In light of this CDC guidance, under the ADA may an employer require antibody testing before permitting employees to re-enter the workplace? 

Answer:

No. An antibody test constitutes a medical examination under the ADA. In light of the CDC’s Interim Guidelines that antibody test results “should not be used to make decisions about returning persons to the workplace,” an antibody test at this time does not meet the ADA’s “job related and consistent with business necessity” standard for medical examinations or inquiries for current employees. Therefore, requiring antibody testing before allowing employees to re-enter the workplace is not allowed under the ADA.  Please note that an antibody test is different from a test to determine if someone has an active case of COVID-19 (i.e., a viral test).  The EEOC has already stated that COVID-19 viral tests are permissible under the ADA.

The EEOC will continue to closely monitor CDC’s recommendations, and could update this discussion in response to changes in CDC’s recommendations.

The full FAQ can be found here.