Back to Vaccines: The Science Behind the Johnson & Johnson Vaccine

Get ready, because it’s time for the latest addition to our vaccine lineup! Image Courtesy of Pixabay.

By Diya Ramesh (‘23)

It’s another quiet Sunday afternoon, when you look at your window, your Google Chrome window, that is, and see something that instantly catches your eye. It’s… the return of the vaccines, the sequel to the sequel, the latest guest at the party! The Pfizer and Moderna vaccines have a new sibling, and its name is the Johnson & Johnson vaccine. 

The vaccine was made by a sector of the Johnson & Johnson company in Belgium called Janssen Pharmaceutica, along with the Beth Israel Deaconess Medical Center. For one dose, clinical trials displayed up to 72% efficacy and even higher numbers for preventing hospitalization or death. Clearly, having another effective vaccine will be critical in humanity’s battle against the COVID-19 pandemic.

Unlike the Pfizer and Moderna vaccines, however, this new vaccine is not an mRNA vaccine. So, what type of vaccine is J&J shot? Well, I’m glad you asked. 

This new vaccine is called a non-replicating viral vector vaccine. In general, viral vector vaccines use another virus (the vector) to transport the main material used to cause an immune response. Typically, this means that the viral vector is carrying a weakened or killed version of the virus that the vaccine is meant to build immunity for. For COVID-19 viral vector vaccines, however, like the J&J one, the viral vector carries genetic material for making the spike protein that the SARS-CoV-2 virus (the virus that causes COVID-19) has, which then causes an immune response. 

Viral vector vaccines can use various different viruses as vectors. These vectors will not make us sick, since they are changed in some way (or sometimes, the virus they use for a vector does not have the ability to bring about disease in humans). For the J&J vaccine, the virus being used is adenovirus 26, which is a virus for the common cold. However, the virus has been changed so that it can go into cells but not recreate itself, meaning that it will not make us ill. As explained by infectious diseases physician at Henry Ford Hospital Mayur Ramesh, the vector is just a delivery service, like Fedex or UPS. This analogy makes sense if extended further. The vector’s job, like that of a delivery service, is solely to deliver the package, which is what you ordered and desire, to you. 

The package itself, in this case, is DNA. Unlike both of the mRNA vaccines for COVID-19, which use mRNA to code for the spike protein, the J&J vaccine uses DNA. Both take advantage of the same process, though, which is the central dogma of biology. The central dogma is how DNA is transcribed into mRNA, which is then translated into proteins. The end goal for both of these vaccines is to make the spike protein, but they just do this by starting at different stages of the central dogma. This also means that for all three vaccines so far, the live virus that causes COVID-19 is not present in any of the vaccines. So, the vaccine will not cause COVID-19. Additionally, the genetic material in it will not change or become part of your DNA.

So, now that we have learned all about the science behind J&J’s vaccine, it’s time for us to give a warm welcome to this latest vaccine. The J&J vaccine is likely to assist numerous people in the world, just like the two that came before it. However, let’s also remember to stay tuned, because who knows when the next vaccine could show up in town? 


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