In News: The Centre is funding the development of four vaccines, which are currently in various stages of human trials
The four vaccines, being funded under Mission Covid Suraksha, were the
DNA-based vaccine candidate by Cadila Healthcare, Gujarat
Protein sub-unit vaccine by Biological E Ltd, Hyderabad
Adenovirus intra-nasal vaccine by Bharat Biotech Ltd, Hyderabad
m-RNA vaccine by Gennova Biopharmaceuticals, Pune.
There are three main approaches to making Vaccine
The whole-microbe approach
Inactivated vaccine: The first way to make a vaccine is to take the disease-carrying virus or bacterium, or one very similar to it, and inactivate or kill it using chemicals, heat or radiation Ex: Flu & polio vaccines. Also, Covaxin is an inactivated viral vaccine.
A live-attenuated vaccine uses a living but weakened version of the virus or one that’s very similar Ex: measles, mumps and rubella (MMR) and the chickenpox vaccine.
Viral Vector Vaccine: This type of vaccine uses a safe virus (different from the one that caused disease) to deliver specific sub-parts – called proteins – of the germ of interest so that it can trigger an immune response without causing disease.
Ex: COVISHIELD: A chimpanzee adenovirus – ChAdOx1 – has been modified to enable it to carry the COVID-19 spike protein into the cells of humans
The subunit approach
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.
Ex: whooping cough, tetanus, diphtheria and meningococcal meningitis.
The genetic approach (nucleic acid vaccine)
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 mRNA (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.
This 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.
