Antibody test does not verify vaccine efficacy

Lower antibody count after jab does not mean poor immunity, say experts

Hyderabad: Mohan Reddy is a worried man nowadays! His cause of worry is that his antibody count is not high, as he anticipated even after taking two doses of vaccine against Covid-19. His firm belief is that post-vaccination, his body would have generated enough antibodies to fight the coronavirus.

But healthcare professionals seek to disagree with such popular notion. They say that the antibody test is meant to ascertain whether those exposed to coronavirus (aka SARS-CoV 2) have developed immune response to the infection. And that it is not a test to verify efficacy of the vaccine.

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Despite this, many in Hyderabad are seen rushing to diagnostic centres for taking a Covid antibody test in the hope of measuring antibodies in their bodies. “Currently antibody tests are not validated to evaluate immunity or protection from Covid-19 infection. Not all antibodies are created equal. The antibodies from past SARS-CoV-2 infection differ from antibodies induced by the Covid-19 vaccines. Therefore, testing for prior infection antibodies would not identify people with antibody protection from immunization,” clarifies US Food and Drug Administration (USFDA).

Moreover, these antibody tests should only be prescribed by experienced health care providers who are familiar with such diagnostics. “We have seen many undergoing antibody tests to check vaccine efficacy and they suffer from anxiety if the test for antibodies is negative. There are different types of antibodies and the test result depends on which antibody it looks for. One should also remember that presence of antibodies is not essential for immunity against the virus as there are many different mechanisms by which a vaccine induces immunity,” explains Dr K Hari Prasad, president of Apollo Group of Hospitals.

The USFDA too has warned against taking antibody tests to measure vaccine-induced antibodies. “The FDA is reminding the public of the limitations of Covid-19 antibody testing and providing additional recommendations about the use of antibody tests in people who received a Covid-19 vaccination,” Tim Stenzel, director of the Office of In Vitro Diagnostics and Radiological Health in the FDA’s Center for Devices and Radiological Health, in a statement said.

Antibody tests can play an important role in identifying individuals who may have been exposed to the SARS-CoV-2 virus and may have developed an adaptive immune response. However, such tests should not be used at this time to determine immunity or protection against Covid-19 and especially after a person has received a Covid vaccination,” USFDA asserts.

Usually, antibodies in the blood are measured from a range of 0 to 1,000 International Units (IU) and a popular perception is that a count below 10 IU after vaccination will not provide enough protection from Covid-19.

However, specialists say that antibody tests can provide the count in IU units, but they will not be able to indicate the T-Cell and B-Cell immunity, which play a vital role in providing protection or immunity from the Covid infection.

 

 

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