Published: 7 July 2021


Viral Vector Vaccines

Viral vector vaccines are a type of vaccine being used to prevent COVID-19 disease. One of these vaccines is called COVID-19 Vaccine Janssen.

What is a viral vector vaccine?

Viral vector vaccines use a modified version of a virus (the vector) to deliver instructions to our cells to make a protein. In the case of COVID-19 Vaccine Janssen, the viral vector belongs to the adenovirus family (not the virus that causes COVID-19). It contains the genetic instructions for our cells to make the spike protein on the surface of SARS-CoV-2 (the COVID-19 virus).

How do viral vector vaccines work?

Vaccines prepare the body to defend itself against a specific disease. Viral vector vaccines contain instructions for making a protein that will be recognised by the immune system as foreign. In this case, the viral vector contains instructions for the spike protein found on the surface of SARS-CoV-2.

The viral vector enters cells in the body and uses the cell’s machinery to make the spike protein. The immune system recognises this protein as foreign and makes immune cells and antibodies which can recognise and attack SARS-CoV-2 via the spike protein.

If the body is later exposed to the SARS-CoV-2 virus, the immune system is prepared to defend the body against illness. As a result, some people may not get infected at all. Others will experience a much milder illness than they would have done without the vaccine.

The COVID-19 Vaccine Janssen viral vector cannot reproduce and cannot cause COVID-19 or other infections. This vaccine can’t alter a person’s DNA.

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