There are several different types of vaccines. Each type is designed to teach your immune system how to fight off certain kinds of germs—and the serious diseases they cause. Lots of discussions are happening across the globe regarding the Covid – 19 vaccine. Let’s consider four types vaccines which are currently being administered / clinical trials are progressing.
A- Whole virus vaccines
Many conventional vaccines use whole viruses to trigger an immune response. There are two main approaches. Live attenuated vaccines use a weakened form of the virus that can still replicate without causing illness. Inactivated vaccines use viruses whose genetic material has been destroyed so they cannot replicate, but can still trigger an immune response.
Example Covaxin by Bharat Biotech, Coronavav by Sinovac, BBIBP-CorV by Sinopham (Beijing)
B- Nucleic Acid
Nucleic acid vaccines use genetic material – either RNA or DNA – to provide cells with the instructions to make the antigen. In the case of COVID-19, this is usually the viral spike protein. Once this genetic material gets into human cells, it uses our cells’ protein factories to make the antigen that will trigger an immune response.
Example mRNA-1273 by Moderna, BNT162b2 by Pfizer/BioNTech are examples of RNA Vaccine. Where as ZyCoV-D by Zydus Cadila is DNA Vaccine.
This contain a modified version of a different virus than the one that causes COVID-19. Inside the shell of the modified virus, there is material from the virus that causes COVID-19. This is called a “viral vector.” Once the viral vector is inside our cells, the genetic material gives cells instructions to make a protein that is unique to the virus that causes COVID-19. Using these instructions, our cells make copies of the protein. This prompts the body to produce antibodies to fight the disease.
Example AZD1222 (Oxford/AstraZeneca) [Whenmanufactured in Serum Institute of India, iti is branded as Covishield], Janssen (by Johnson & Johnson), Sputnik V (By Gamaleya)
D-Protein Subunit Vaccine
Rather than injecting a whole pathogen to trigger an immune response, subunit vaccines (sometimes called acellular vaccines) contain purified pieces of it, which have been specially selected for their ability to stimulate immune cells. Because these fragments are incapable of causing disease, subunit vaccines are considered very safe.
Example NVX-CoV2373 by Novavax which is undergoing clinical trial