Understanding Viral Vector COVID-19 Vaccines

The Johnson & Johnson Janssen vaccine, a viral vector vaccine, is among the COVID-19 vaccines authorized for emergency use in the United States.

How Viral Vector Vaccines Work

COVID-19 viral vector vaccines use a modified version of a different virus (a vector virus) to deliver important instructions to our cells.

1. First, COVID-19 viral vector vaccines are given in the upper arm muscle. The COVID-19 vector virus is not the virus that causes COVID-19, but a different, harmless virus. It enters the muscle cells and uses the cells’ machinery to produce a harmless piece of what is called a spike protein. The spike protein is found on the surface of the virus that causes COVID-19.
2. Next, the cells display the spike protein on their surface, and our immune system recognizes that the protein doesn’t belong there. This triggers our immune system to produce antibodies and activate other immune cells to fight off what it thinks is an infection. This response is what your body might do if you got sick with COVID-19.
3. At the end of the process, our bodies have learned how to protect us against future infection with the virus that causes COVID-19. The benefit is that we get this protection from a vaccine, without ever having to risk the serious consequences of getting sick with COVID-19. Any temporary discomfort experienced after getting the vaccine is a natural part of the process and an indication that the vaccine is working.

Viral Vector Vaccines Have Been Rigorously Studied for Safety

Viral vector vaccines for COVID-19 have been held to the same rigorous safety and effectiveness standardsexternal icon as all other types of vaccines in the United States. The only COVID-19 vaccines the U.S. Food and Drug Administration (FDA) will make available for use in the United States (by approval or emergency use authorization) are those that meet these standards.

While COVID-19 vaccines were developed rapidly, all steps have been taken to ensure their safety and effectiveness.

How Viral Vector Vaccines Have Been Used During Recent Disease Outbreaks

Scientists began creating viral vectors in the 1970s. Besides being used in vaccines, viral vectors have also been studied for gene therapy, to treat cancer, and for molecular biology research. For decades, hundreds of scientific studies of viral vector vaccines have been done and published around the world. Some vaccines recently used for Ebola outbreaks have used viral vector technology, and a number of studies have focused on viral vector vaccines against other infectious diseases such as Zika, flu, and HIV.