Mumbai: Surge in spike protein antibody tests among vaccine beneficiaries

After taking Covid-19 vaccines, many beneficiaries are undergoing spike protein antibody test which detects proteins created by the immune system to fight the Sars-CoV-2 virus

After taking Covid-19 vaccines, many beneficiaries are undergoing spike protein antibody test which detects proteins created by the immune system to fight the Sars-CoV-2 virus. Private laboratories have observed around three-fold rise in people opting for the antibody test as compared to February this year.

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Initially only healthcare workers (HCL) and frontline workers (FLW) were taking the tests, but over the past few months, private laboratories are seeing a number of general public opting for the test to determine the development of neutralising antibodies after vaccination. However, doctors have overruled the need for testing post-vaccination.

Since May last year, Dr Vikrant Singh, 38, has been working with the Brihanmumbai Municipal Corporation (BMC) in city slums. He is responsible for tracing close contacts of infected patients in slums of Govandi, Chembur and surrounding areas. Despite wearing personal protective equipment (PPE), there is always a chance of contracting the infection on the field. So, he stayed away from his family in an empty flat.

A fortnight after taking the second jab of vaccine on February 12, he undertook the spike protein antibody test. “My test revealed that my antibody presence was high which gave me some assurance. Finally, after months, I could hug my 70-year-old mother who has diabetes,” he said.

The spike protein antibody test has gained quite a buzz among vaccine beneficiaries. Considering the rise in demand for the test, several private labs such as SRL Diagnostic, Metropolis Healthcare, Dr B Lal Clinical Laboratory among others have started the facility. The test costs between ₹500 and ₹1,400.

“The test was well-received by the medical fraternity and healthcare workers including doctors, who were among the first to be vaccinated. With the vaccination drive open to the public, there has been a growing interest among common people to go for the spike protein antibody test. Between February and April, there has been a three-fold increase in people opting for the test. They are keen to know how their bodies are reacting to the vaccine in terms of development of antibodies,” said Anand K, chief executive officer (CEO), SRL Diagnostics.

Thyrocare Diagnostics has recorded almost 100% growth in the demand of testing between February and April. It has also been observed that the antibodies remain in the body for three to 12 months, though the lab has not made any study on it.

“The beneficiaries are interested to know how their bodies are producing the antibodies in reaction to the jab. This provides an assurance to the public. Though the test does not help to determine the efficiency of any vaccine, it helps understand the level of immunity obtained,” said Chandrashekhar Mani, vice-president (operations), Thyrocare.

Antibodies are protective proteins produced by the immune system in response to the presence of a foreign substance. These antibodies are produced in the body in two ways — when it is exposed to a virus and after getting a vaccination. The antibody produced after the vaccination neutralises the virus.

“Viruses have two different types of proteins — spike protein and nucleo-capsid protein. Spike protein remains on the surface of the virus while nucleo-capsid protein is found inside the virus. The viruses generally enter the human cell through the spike protein domain. Thus, most vaccines such as Covishield have been designed to target the spike protein. This antibody test helps in the detection of the presence of antibodies specific to the Sars-CoV-2 spike protein,” said Dr Sanjay Ingle, zonal technical head (west) and consultant pathologist, Apollo Diagnostics.

Spike protein antibodies are generally developed after two weeks of taking the second dose. Dr Anupa Dixit from Suburban Diagnostics said, “To get an assured report, the test needs to be done after 15days of taking the second jab.”

No need to do spike protein test post-vaccination

However, a certain section of the medical fraternity has advised not to take the test after taking the jabs. The US Food and Drug Administration (FDA), on its official website, has not recommended the test post-vaccination to determine the level of immunity or protection from Covid-19.

Dr Rahul Tambe, senior consultant, Internal Medicine and Infectious Disease, Nanavati Max Super Speciality Hospital, said, “Individuals should not use the antibody test as a tool to gauge their immunity. Antibody level alone is not a reflection of one’s immunity or protection against Covid-19. Several other physiological factors play a vital role in building an immune response.”

Bharat Biotech’s Covaxin has an efficacy rate of 81%, preliminary data from its phase three trial shows. Clinical trials of Oxford-AstraZeneca’s Covishield vaccine showed that when people were given a half dose and then a full dose, the effectiveness hit 90%.

“These vaccines have undergone clinical trials and then been given approval from the Drugs Controller General of India, so there is no point in undergoing spike protein antibody tests after vaccination,” said Dr Shashank Joshi, part of the state’s Covid task force.

Rise in IgG antibody tests in second wave

Last year, a large number of people underwent Immunoglobulin G (IgG) antibody tests to understand if they had ever been infected with the virus.

As per the data shared by Thyrocare, on an average around 2,400 people undertook the test daily last year. However, with the fall in the pandemic curve, the number decreased to 1,000 tests per day in January. Since February, when the second wave started, the number rose to an average of 3,000 tests per day. In April, they conducted 4,000 tests per day.

When the body comes in contact with any diseases-causing pathogens, the first antibody produced by the internal system is Immunoglobulin M (IgM) and later IgG is produced by the immune system. IgG plays a role in creating memory cells that remain in the body to help fight the virus in case of reinfection.

“Last year, many Covid-recovered people increasingly opted for IgG antibody tests. The major motivation behind opting for IgG antibody test was to ascertain whether they could qualify to be plasma donors. However, as the impact of the first wave tapered and cases decreased, the demand went down. With the current wave of Covid-19, the demand for antibody testing has again gained momentum,” said Anand K.