Explainer on how COVID-19 Vaccines are Developed

Prof. Walter Jaoko

Professor of medical microbiology and tropical medicine, Director KAVI Institute of Clinical Research, University of Nairobi

There are different ways of developing vaccines. You can weaken a virus, so it is still alive but is weakened, that is what we call attenuation. Therefore, it cannot cause disease in a human being. But when somebody is given the vaccine, the body stimulates responses thinking that it has become infected and those antibodies and cells are, therefore, ready in the event that you face the real virus.

Secondly, you can take just the portion of the virus, what we call the spike protein, and develop a vaccine out of it. The portion that you are taking is what is described as the plasmid (fingerprint of the virus). So, when the body sees that plasmid at the surface, it thinks it has seen the virus and therefore produces responses to fight it either as antibodies or as white blood cells.

The third way of making a vaccine, and this is what is being used largely in Africa, is called a vectored vaccine, where you take the plasmid and you put it in another vector, which is a weakened virus that does not cause infection in human being, that makes the body recognize that plasmid much faster and in a robust way. Therefore, the immune responses are generated in larger quantities and faster than if you use a plasmid.

The final one, which we still don’t have in Africa but few countries are using it, is a new technology called the messenger RNA technology. This is what is used in some vaccines like Moderna and Pfizer vaccines, where you take the message that the virus uses to prepare spike protein and that is what you inject into a human cell. The human cell reads that message, prepares this spike protein on its surface and then the same human being’s immune response recognizes that protein and therefore produces antibodies and white blood cells to fight the COVID virus. So, the body is therefore protected that way.






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