The Value of Spike Antibody Assays in the Fight Against COVID-19

February 5, 2021

Consider this hypothetical scenario: Jane Smith, a Registered Nurse who works for a major healthcare organization, is scheduled to receive the COVID-19 vaccine through her workplace next week. She’s never had a COVID-19 test or experienced any symptoms of the virus, but given her position as a frontline worker, she’s wondering whether she’s previously been exposed and has already developed some degree of immunity.

As COVID-19 vaccinations become deployed on a more widespread basis, antibody testing is poised not only to play a significant role in informing patients as to their level of protection against the virus, but also to provide useful data to researchers and clinicians as to the long-term effectiveness of inoculations.

There are two main categories of SARS-CoV-2 antibody tests on the market, both offering different utility benefits. A qualitative test provides a simple yes-or-no answer as to whether COVID-19 antibodies are present; whereas quantitative and semi-quantitative tests measure the amount of antibodies in a patient’s blood sample. And to offer even more definitive data about the body’s immune response to the virus, a semi-quantitative spike assay targets the spike protein that binds to the host cell receptor (the protein most vaccines are targeting).

On Dec. 2, Roche’s Elecsys® Anti-SARS-CoV-2 S antibody test received Emergency Use Authorization from the U.S. Food and Drug Administration to measure the level of antibodies in people who’ve been exposed to the virus. This semi-quantitative spike test provides a numerical result describing the concentration of antibodies, as well as a qualitative result. A few days later, Roche announced a partnership with Moderna to include SARS-CoV-2-S antibody testing in ongoing COVID-19 vaccine trials to establish a correlation between vaccine-induced protection and levels of anti-receptor binding domain antibodies.

Since Jane has never experienced any COVID-19 symptoms, a spike assay could determine if antibodies are present, indicating she has previously been exposed to the virus. Or, Jane could receive an antibody spike test after receiving the COVID-19 vaccine, which would provide Jane the peace of mind in knowing that the vaccine and her immune response are working as they should to provide protection.

As months go by, semi-quantitative antibody tests can reveal valuable information about titer levels over time, revealing how long vaccine protection lasts and to what degree. With so much still unknown about the COVID-19 virus, this data is of great interest to researchers and may help to steer future decisions about vaccine utility and other treatments. Semi-quantitative assays may also help to guide the allocation of plasma donations from recovered COVID-19 patients to current patients by identifying donors that already have antibodies to SARS-CoV-2 virus. 

Patients should talk to their healthcare providers to determine whether COVID-19 antibody testing is appropriate, and if so, at what point in the vaccine progression and which assays to use.