Principle

The basic principle of vaccination is ''memory'' of the immune system. Vaccines let the immune system to learn how to fight the future onslaught of that pathogen for which vaccine is being given. The body prepares antibodies in response to vaccination and remembers this act. When the related pathogen attacks in the future, the immune system uses its ''memory'' to fight the infection. Hepatitis B vaccine is produced from yeast.

Working

Vaccines contain weakened or inactive parts of a particular organism (antigen) that triggers an immune response within the body. Newer vaccines contain the blueprint for producing antigens rather than the antigen itself. Regardless of whether the vaccine is made up of the antigen itself or the blueprint so that the body will produce the antigen, this weakened version will not cause the disease in the person receiving the vaccine, but it will prompt their immune system to respond much as it would have on its first reaction to the actual pathogen.

Some vaccines require multiple doses, given weeks or months apart. This is sometimes needed to allow for the production of long-lived antibodies and development of memory cells. In this way, the body is trained to fight the specific disease-causing organism, building up memory of the pathogen so as to rapidly fight it if and when exposed in the future.

Approaches adopted by India 

There are three main approaches to designing a vaccine. Their differences lie in whether they use a whole virus or bacterium; just the parts of the germ that triggers the immune system; or just the genetic material that provides the instructions for making specific proteins and not the whole virus.

• Whole virus vaccines use a weakened (attenuated) or deactivated form of the pathogen that causes a disease to trigger protective immunity to it. There are two types of whole virus vaccines. Live attenuated vaccines use a weakened form of the virus, which can still grow and replicate, but does not cause illness. Inactivated vaccines contain viruses whose genetic material has been destroyed by heat, chemicals or radiation so they cannot infect cells and replicate, but can still trigger an immune response. COVAXIN
  developed by the Bharat-Biotech, is aninactivated vaccine which is developed by inactivating the live microorganisms that cause the disease.
• A subunit vaccine is one that only uses the very specific parts (the subunits) of a virus or bacterium that the immune system needs to recognize. It doesn''t contain the whole microbe or use a safe virus as a vector. The subunits may be proteins or sugars. Most of the vaccines on the childhood schedule are subunit vaccines, protecting people from diseases such as whooping cough, tetanus, diphtheria and meningococcal meningitis. CORBEVAX, developed by Biological E Limited, is a recombinant protein sub-unit vaccine developed from the Receptor Biding Domain (RBD) of the spike protein on the viral surface is adjuvanted with CpG 1018 and alum.
• The genetic approach (nucleic acid vaccine) - Unlike vaccine approaches that use either a weakened or dead whole microbe or parts of one, a nucleic acid vaccine just uses a section of genetic material that provides the instructions for specific proteins, not the whole microbe. DNA and RNA are the instructions our cells use to make proteins. In our cells, DNA is first turned into messenger RNA, which is then used as the blueprint to make specific proteins. 
  • A nucleic acid vaccine delivers a specific set of instructions to our cells, either as DNA or mRNA, for them to make the specific protein that we want our immune system to recognize and respond to. 
  • The nucleic acid approach is a new way of developing vaccines. Before the COVID-19 pandemic, none had yet been through the full approvals process for use in humans, though some DNA vaccines, including for particular cancers, were undergoing human trials. Because of the pandemic, research in this area has progressed very fast and some mRNA vaccines for COVID-19 are getting emergency use authorization, which means they can now be given to people beyond using them only in clinical trials.
  • GEMCOVAC-19 is the very first mRNA vaccine developed in India and only third mRNA vaccine to be approved for COVID-19 in the world.

India has always supported the research, development and manufacturing of COVID-19 vaccines under the “Make-in-India” and “Make-for-World” Strategy, embarked on the use of cutting-edge technologies like CoWIN.