The science of COVID-19 vaccines and the critical role of neutralising antibodies

Dr Abha K Sabhikhi, MD Pathology, Advisor and Mentor, SRL Technical CoE & Academics, SRL Diagnostics analyses that antibody testing during the period of COVID-19 vaccination is crucial to track and measure the level of antibodies a vaccine has generated in the body

The COVID-19 vaccination drive has been initiated on a war footing in India, at a scale unmatched in the world. In just over two months, India has vaccinated around 4 crore people, with the drive achieving a pace of 20 to 30 lakh vaccines per day.

Keeping the spirit of vasudhaiva kutumbakam (the world is one family) central to the vaccination mission, our country has gained international goodwill for supplying over 596 lakh ‘Made in India’ vaccine doses to 73 nations in the world.

Rising COVID complacency

Despite lakhs being vaccinated daily, India also happens to be facing a new wave of COVID-19. A major reason attributed to the new wave is that with vaccine in sight, COVID-fatigued people have begun behaving negligently, mistakenly believing that vaccination is a sure-shot solution to the public health crisis. Consequently, people have stopped following COVID appropriate measures.

Also, many people after being vaccinated are becoming negligent towards COVID-19 prevention measures. As this can prove to be dangerous and counterproductive to the entire effort of vaccination, it is important for the medical community to spread awareness on the real role of vaccination.

The need to be on-guard despite vaccination

Finding a vaccine for any disease is a complex process and needs years of scientific research and testing. The creation of COVID vaccines in record time is, indeed, a major feat for mankind. However, the science of diseases and vaccination is not as simplistic as we would like to believe. The following are some reasons why people need to continue with COVID appropriate behaviour.

Considering the vast population that is being inoculated, it is too early to say how effective vaccines would be in neutralising the infection and in containing its spread. The efficacy of vaccines against all the variants of the virus spread across the globe is also not completely known. Furthermore, the strength and permanency of the immunity gained by the vaccine is yet to be conclusively tested.

Understanding the working of COVID-19 vaccines

COVID-19 vaccines help our bodies develop immunity to the virus that causes COVID-19 without the individual having to get the illness. Different types of vaccines work in different ways to offer protection. But with all types of vaccines, the body is left with a supply of “memory” B-lymphocytes as well as T-lymphocytes that will remember how to fight that virus in the future. It typically takes approximately two weeks after vaccination for the body to produce an immune response. Therefore, it is possible that a person could be infected with the virus that causes COVID-19 just before or soon after vaccination. In such a situation the individual will develop the disease as the vaccine did not have adequate time to provide protection.

The Indian Government has approved two types of vaccines. Presently, the inoculation drive in India involves administration of two doses of a vaccine at a gap of 4 to 8 weeks depending upon which vaccine is being injected. A lot depends on the quality of antibodies developed after each dosage of these vaccines. The vaccines administered in India either use a whole-virion inactivated vero cell technology which introduces lab-isolated dead coronavirus in the body or they introduce a mix of spike protein extracted from coronavirus and added to a common cold adenovirus.

After being injected into the body, these foreign viral components provoke the human immune system to activate antibodies. When faced by a real COVID infection, the antibodies attach to the virus cells, mark them for killing, and prevent them for infecting healthy cells. Therefore, the production of quality antibody is critical to the success of vaccination.

The need for antibody testing post vaccination

There are several factors why despite vaccination, the COVID-19 vaccine may fail to trigger the production of enough antibodies. Some of the known factors associated with a low immune response post vaccination include old age, compromised immunity, various comorbidities, drinking alcohol regularly post vaccination, genetic background and even previous infections.

So how does can one know whether the vaccination has led to an adequate production of antibodies? It is through an antibody test that one can measure the level of antibodies produced in the body after vaccination. The test needs to be taken two weeks after each round of vaccination.

Which antibody test works?

The need is to check for the development of neutralising antibodies that are protective against disease. This is best done with the new antibody test, also known as the SARS-COV-2 Spike Protein Antibody test that detects neutralising antibodies. This is not to be confused with the regular Total and IgG antibody test being used mainly in serological surveys for tracking COVID spread in the population for epidemiological purposes.

The SARS-COV-2 Spike Protein Antibody test is designed to determine the protective immunity level achieved post vaccination. The test determines antibodies against the viral spike protein that binds to the human cells to gain entry into the body. Production of neutralising protective antibodies against SARS-CoV-2 Spike protein correlates best with the protection gained by the individual post vaccination. Basically this test answers whether the individual has protective antibodies that will fight the infection if exposed to the virus.

The critical role of antibody testing

The new antibody testing has an important role to play at an individual and community level. The test if conducted on a good sample size of individuals at various stages of vaccination can evaluate the effectiveness of the vaccination drive. It can identify possible shortfalls, and strengthen the programme.

At an individual level, the knowledge of protective immunity is reassuring and gives confidence in the process. Detection of a low immunity level after vaccination will help people take appropriate measures of consulting their healthcare provider and continue to be cognisant towards COVID appropriate measures.

Furthermore individuals with high levels of neutralising antibodies could be potential candidates for plasma donation to severely infected COVID patients. Clearly selecting a specific appropriate antibody test post vaccination is critical to our fight against the pandemic.