Type of vaccine

Viral vector (genetically modified virus)

The COVID-19 virus uses proteins on its outer surface, called spike proteins, to enter the body’s cells and cause disease. 

The vaccine is made up of another virus (of the adenovirus family) that has been modified to contain the gene for making the SARS-CoV-2 (COVID-19) spike protein (the part of the virus that allows it to enter human cells). The adenovirus itself cannot reproduce and does not cause disease. 

Once it has been given, the vaccine delivers the SARS-CoV-2 gene into cells in the body. The cells will use the gene to produce the spike protein. The person’s immune system will treat this spike protein as foreign and produce natural defences − antibodies and T cells − against this protein. 

If, later on, the vaccinated person comes into contact with SARS-CoV-2, the immune system will recognise the virus and be prepared to attack it: antibodies and T cells can work together to kill the virus, prevent its entry into the body’s cells and destroy infected cells, thus helping to protect against COVID-19.

Type of vaccine

The jabs are known as a messenger RNA (mRNA) vaccine. It uses synthetically produced genetic material called mRNA, which encodes the instructions to produce the SARS-CoV-2 (COVID-19) spike protein (the part of the virus that allows it to enter human cells).

The injection inserts this mRNA into the body. This then enters cells, which read the genetic code and start producing the virus protein – thus triggering a response by the immune system and coaching it to fight a future infection.

The mRNA molecule is not injected directly into the body, but is wrapped in oily bubbles made of lipid nanoparticles, to prevent our natural enzymes from breaking it down.

The jab uses mRNA produced in the lab by a template DNA, and doesn’t use a virus, unlike conventional vaccines which are produced using weakened forms of the virus. This can make the rate at which it can be produced or modified dramatically accelerated.

The difference between the Pfizer / BioNTech and Moderna vaccines to the Oxford University / AstraZeneca vaccine is that the former uses mRNA as its platform, while the latter uses DNA, which is delivered to the cells by using a weakened version of a common cold virus.