Vaccinated? Now don’t go looking for antibodies

A woman gets vaccinated at a city hospital. File pic

An antibody test after vaccination is no yardstick to judge protection against Coronavirus, experts have cautioned, especially since there have been instances of fully vaccinated people finding no antibodies in their system, raising doubts on the effectiveness of vaccines. The warning comes at a time when antibody tests are being advertised for home-use. Experts say incorrect interpretation of the test results might prompt some fully vaccinated people to lower their guard against Covid-19.

"While a positive antibody test result can be used to help identify people who may have had prior SARS-CoV-2 infection or resulted from vaccine shots, more research is needed to know whether this test can pick up yet an undetermined category of neutralising antibodies that will provide protection for the future. That is because the currently authorised SARS-CoV-2 antibody tests have not been evaluated to assess the level of protection provided by an immune response to Covid-19 vaccination," says Dr Subhash Hira, Professor of Global Health at the University of Washington-Seattle.

Dr Hira said, "If antibody test results are interpreted incorrectly, there is a potential risk that people may take fewer precautions against SARS-CoV-2 exposure even after completing the vaccine shots. Thus, taking fewer steps to protect against SARS-CoV-2 can increase their risk of SARS-CoV-2 infection and may result in the increased spread of SARS-CoV-2."

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The expert made a few recommendations for those who have had an antibody test:

1. Antibody tests help healthcare providers identify whether someone has antibodies to SARS-CoV-2, indicating a prior infection with the virus. However, more research is ongoing to understand the meaning of a positive or negative antibody test, including in people who received a Covid-19 vaccination.

2. If you have not been vaccinated: Positive result does not mean you have a specific amount of immunity or protection. It means that it is possible you were previously infected with the SARS-CoV-2 virus.

3. If you are vaccinated: Covid-19 vaccine shots may also cause a positive antibody test result for some but not all brands of antibody tests.

Calling the correlation between antibody test results and protection due to vaccines "premature", Dr Hira said, "I feel that SARS-CoV-2 antibody tests should be ordered only by health care providers who are familiar with the use and limitations of the test rather than just through an access-online product."

Dr Wiqar Shaikh, Professor of Medicine, Grant Medical College and Sir J.J. Group of Hospitals, said the human body has an efficient "immune system" to fight off bacteria and viruses and it produces "neutralising antibodies" helpful only for a short period--between the virus entering the body and then entering the cells of an individual. Inside the cells, antibodies have no role and it is the job of T-cells to kill the virus infected cells.

Dr Subhash Hira, professor of Global Health at the University of Washington-Seattle

Dr. Shaikh added that in India, Covid-19 is being caused by a "mutation" of the original virus. He explained that when a virus multiplies inside a cell, it makes an error during multiplication, which results in a change in its genetic code. Mutation makes it more difficult for the virus to be detected and treated and results in a spike in cases, increased hospitalisation and more deaths. He emphasised that antibodies are unable to attack a mutated virus and can't prevent it from entering the cell.

Dr Shaikh expressed surprise over media reports discussing the role of antibodies in Covid-19 infection, particularly following vaccination. He said he is amused that people sued vaccine manufacturers saying their shots did not produce antibodies. The role of T-cells which is of paramount importance in Covid-19 infection and protection following vaccination has been completely ignored, he added.

Dr Shaikh cited a November 2000 publication in the Journal of Virology (USA) which says that "antibodies play little or no role in controlling viral infections".

He quoted another article in Science Daily of March 2012 that said "antibodies are not required for immunity against viruses". A publication from the Centre for Evidence Based Medicine, Oxford University in October 2020, said that "it is the T-cell response which bodes well for long-term immunity in Covid-19 infection", he said.

In July 2020, ‘Nature' journal used data from patients infected with the older SARS-CoV virus in 2003 to conclude that the infection induced a durable T-cell response lasting up to 7 years but did not produce a long-term antibody response. An important finding from this study was that the T-cells from the 2003 infection were shown to kill Covid-19 virus, 17 years after the original infection.

It is important for Covid-19 vaccines to stimulate a robust T-cell response, he said, adding, "Measuring antibodies after a vaccine dose is of little value and it is imperative to study T-cells following administration of Covid-19 vaccines."