Janssen COVID-19 Vaccine (Johnson & Johnson)

How does the Janssen COVID-19 vaccine work?


COVID-19 Vaccine Janssen is a vector vaccine made up of another virus (an adenovirus type 26) that has been modified to contain the gene for making the SARS-CoV-2 spike protein (glycoprotein (Ad26.COV2-S). This is a protein on the SARS-CoV-2 virus which it uses to enter the body’s cells.

Adenovirus type 26 is a nonreplicative human adenovirus. The virus in the vaccine does not cause disease. Vaccinating with this weakened adenovirus trains the body to recognize SARS-CoV-2 virus and develop an immune response against its spike protein that helps to prevent disease if SARS-CoV-2 virus later enters the body.

The adenovirus passes the SARS-CoV-2 gene into the vaccinated person’s cells. The cells can then use the gene to produce the spike protein. The person’s immune system will recognise the spike protein as foreign and produce antibodies and activate T cells to target it. Later, if the person comes into contact with SARS-CoV-2 virus, the person’s immune system will recognise the spike protein on the virus and be ready to defend the body against it.

Janssen COVID-19 vaccine:

  • contains a weakened adenovirus that carries the gene to produce the SARS-CoV-2 spike protein
  • trains the vaccinated person’s body to fight off the SARS-CoV-2 virus

Strategic Advisory Group of Experts on Immunization (SAGE) interim recommendations for use of COVID-19 vaccines: