Covid-19 antibody test not to be used to evaluate immunity, says doctor

Antibodies are proteinaceous substances made by our immune system to fight infections like viruses and may help to protect against future occurrences by those same infections.

Amid the rising cases of Delta and Delta mutations of the coronavirus (Covid-19), the Hindustan Times spoke to Dr Ravi Shekhar Jha of Fortis Escorts hospital in Faridabad, National Capital Region, to talk about the antibodies test and how one can analyse the results by themselves. He said whether a person who recently recovered from the infection caused by the Delta variant have enough antibodies to fight the Delta Plus variant, a dangerous mutation of the Covid-19 virus. The government declared Delta plus a "variant of concern" on June 22 as the cases continued to rise in the country.

It is not advisable to get your antibody level tested after recovery or after vaccination. (AFP file)

Jha is the senior consultant and head of the Pulmonology department at the Fortis hospital.

Here is all your FAQs regarding the anti-body tests answered:

Q: Many Indians are getting antibody tests conducted after recovering from Covid-19 or after getting vaccinated. Should one get these tests done to start a normal life?

A: The current recommendation is that the SARS-CoV-2 antibody tests should not be used to evaluate the level of immunity or level of protection of someone from Covid-19, and especially after the Covid-19 vaccination. A positive antibody test result can be used to help identify people who may have had prior Covid-19 infection, antibody response after Covid-19 vaccination is still under evaluation. If antibody test results are not interpreted with clinical parameters, there is a potential risk that people may lower their guard. This can increase their risk of getting SARS-CoV-2 infection and may result in the increased spread of SARS-CoV-2.

Q: How do antibodies help us fight against the coronavirus and for how long do they stay in our body?

A: Antibodies are proteinaceous substances made by our immune system to fight infections like viruses and may help to protect against future occurrences by those same infections. Antibodies can take several days or weeks to develop in the body following exposure to a SARS-CoV-2 (Covid-19) infection and it is presently not known how long they stay in the blood.

Q. Is it possible to measure the level of antibodies in our body and for how long would they stay?

A: Yes, the level of antibodies can be measured, but, at this time, it is not recommended to measure the level of SARS-CoV-2 antibody tests as an indication of a specific level of immunity or protection from SARS-CoV-2 infection after the person has received a Covid-19 vaccination. While a positive antibody test can indicate an immune reaction or response has occurred (seroconversion), and failure to detect such a response may suggest a lack of immune response, data to date is insufficient to confirm or negate this. To date, SARS-CoV-2 antibody tests are not validated to evaluate specific immunity or protection from SARS-CoV-2 infection.

Q: Would the vaccine induced antibodies or immunity stay forever or would we be required to take the doses even after 2 rounds of shots?

A: Vaccination may cause a positive antibody test result for some but not all antibody tests would give similar results. You should not interpret the results of your antibody test as an indication of a specific level of immunity or protection from SARS-CoV-2 infection.

For example, Covid-19 mRNA vaccines induce antibodies to the spike protein and not to nucleocapsid proteins that are usually detected only after someone has had a natural infection.

Therefore, Covid-19 vaccinated people who have not had previous natural infection will receive a negative antibody test result if the antibody test does not detect those antibodies which are induced by the specific Covid-19 vaccine.

Q. There are several types of antibody tests available in the market. Should one opt for an IgG test, IgM, or a total antibody test?

A: It depends on various parameters. However, in general, IgG antibody response is needed to ward off future infection. IgM antibody indicates current infection. Antibody result is always analyzed in a clinical context, so self-testing and interpretation should always be avoided.

Q: How can oneself analyze the antibody test result?

A: Self-analysis of antibody testing should always be avoided. As mentioned in the earlier questions, the natural infection may produce a different types of antibody responses, different types of vaccines produce a different antibody response. Therefore, it has to be interpreted by a clinician, in context with the clinical and vaccination profile of the patient.

Q: When is the ideal time to get an antibody test done after both recovery and full vaccination?

A: Patients usually begin to develop antibodies 1-3 weeks after symptoms. However, it is not advisable to get your antibody level tested after recovery or after vaccination. Antibodies level after natural infection may give a false sense of protection. Also, even without natural Sars COV 2 infection, antibodies levels may be falsely raised due to infection by other Coronaviruses (like the common cold).

Antibody interpretation after vaccination needs to be interpreted only by a health care worker, since it depends on many factor, including the type of vaccine that you have taken.

Q: Can a person who has recovered from Delta variant have enough antibodies to fight the Delta Plus variant?

A: To date, it is unclear that if the person who has recovered from the delta variant is fully protected against delta plus or not, but the evidence suggests that the best way to be protected against delta plus variant is to get vaccinated.

Q: Do antibody immunity levels remain the same for all or do they vary based on comorbidities and age?

A: Antibody level fades with time. The level of immune reaction or antibody formation depends upon various factors, like your age, immunocompromised status, and comorbidities, including your dietary habits. Also, younger people get higher antibody responses than the elderly.

Q: How accurate are the antibody tests results? Do they have any limitations?

A: The accuracy of the antibody tests is questionable. The test can be false positive (like falsely raised when someone never had a Covid infection of vaccination, still the antibodies levels are falsely high due to infection by non-SARSCOV 2 corona virus). It can also be falsely negative, like if taken too early in the course of the disease, or if someone is immunocompromised.