What is the difference between an mRNA and a viral vector vaccine?

The surface of the COVID-19 virus features a specific type of protein known as ‘spike proteins’. mRNA and viral vector vaccines contain information that instructs cells on how to produce spike proteins. Once spike proteins are produced by the cells, the immune system recognizes that these proteins are alien to the body. It then produces antibodies that are effective at preventing the spread of the disease in the body. 

Although Both mRNA and viral vector vaccines are used against the virus that causes COVID-19, they work differently. 

In mRNA vaccines, the instructions are mRNA or messenger RNA, which is the genetic material that tells cells how to make proteins. Tiny lipid molecules that surround the mRNA help the mRNA enter the cells directly. When the cells create spike proteins, the mRNA is broken down by the body and removed. This happens within a few days after getting the mRNA vaccination. 

Viral vector vaccines use a harmless virus as a delivery system. In these vaccines, spike protein DNA is inserted inside a modified version of a harmless virus such as adenovirus. This harmless loaded virus acts as a vector and delivers the DNA instructions to the cell, triggering the immune system to produce antibodies to fight off infections. Once the cells produce spike proteins, the vector virus is broken down by the body and removed. This happens within a few days after vaccination.