COVID-19: New test to measure vaccine-induced immune response

Today, the vaccine is the only available protection against the coronavirus but how protected are you after the jab or more specifically, how has the body’s immune system responded to the vaccine? The answer lies in tracking and measuring the level of antibodies a vaccine has generated in the body. The antibodies in the body broadly come in two forms – ones that bind to a pathogen but do not necessarily hinder the spread of infection and there are others that neutralize the pathogen and protect the cell. Late last year, Basel-headquartered healthcare major Roche came up with a test to measure the level of antibodies in people who have been exposed to the SARS-CoV-2 virus. It is now being deployed by select diagnostic labs in India with SRL Dr Avinash Padke Labs in Mumbai among the first ones to roll it out.

Speaking to Financial Express Online, Dr Avinash Phadke founder, Dr Avinash Phadke Labs and president, SRL Diagnostics, says “there are many people with a compromised immune system and some may not have adequate antibody response even after vaccination.”

For instance, he explains: “there are many people who are diabetic, elderly or even frail individuals in some cases who may not produce an adequate amount of antibodies and therefore it becomes important to track their level of immunity after the vaccination.”

Giving an example, he says, “suppose there is a plasma donor to a COVID-19 patient, it will be important to do this test because unless the donor has neutralizing antibodies the plasma may not be of much use to the patient.”

So what if the test shows poor immune response then, the doctor says, “one needs to then examine whether they need to take an additional dose of vaccination (more than what is normally administered) but more importantly, they need to be doubly careful in taking the precautions to avoid any exposure because of the risks of a lower immune response in the body.”

This SARS-COV-2 Spike Protein Antibody test, he explains, “is directed against the spike protein component of the covid virus, which also happens to be the virulent part of the virus. The antibody produced after the vaccination neutralizes the virus and is therefore called the neutralizing antibody.”

The purpose of this test, which costs Rs 1,400, he says, “is not to find out about the past exposure, which happens to be an incidental outcome of the test but the main aim is to get a picture of the level of immunity, which the earlier general antibody test did not tell us.”

Experts are today keen more to see studies that can come up with findings on the long-term correlation between antibody levels and protection. Or as one well-known medical expert who preferred to stay anonymous says, “whether the level of antibody detected by this test correlates to the efficacy of the COVID vaccine is yet to be determined.” There is also the element that human immune responses are shaped by myriad factors including age, gender, genetic background, environmental exposures, and even previous infections.

Dr Phadke says, he does intend to study the long-term correlation between the levels of antibodies and protection. He also reminds us that this test detects antibody-mediated immunity and not the cell (T-cell) mediated immunity. There is as yet, he says, no test to track that.