What’s in Johnson & Johnson’s Covid-19 Vaccine?

Proven vaccine technologies reveal a safe and effective Covid-19 vaccination

Source: https://commons.wikimedia.org/wiki/File:Adenovirus_D26_wiki.png

As vaccines begin to roll out across the United States, a third contender has risen through the ranks as a viable candidate for Covid-19 protection. The Johnson & Johnson AD26.COV2.S vaccine offers strong protection against the SARS-CoV-2 virus in only a single shot.

With the vaccine inching closer to public availability, this article details the exact ingredients included in each shot.

The basics

The AD26.COV2.S vaccine utilizes adenovirus technology to expose human immune systems to SARS-CoV-2 virus antigens. This is achieved by cloning a copy of DNA that encodes the SARS-CoV-2 spike protein into a loop of DNA called a plasmid, which is then housed within a modified adenovirus.

Once introduced into the body, the modified adenovirus binds and enters human cells. At this point, the body of the virus essentially disintegrates, allowing the genetic material within to travel into the nucleus of human cells. Once there, native enzymes that transcribe DNA into mRNA take over and start to turn out strips of mRNA that code for the spike proteins. These mRNA strips — called transcripts — are then translated into the spike protein. Finally, the spike proteins are then packed and sent to the outer cell membrane where they can be accessed by the host immune system.

Adenovirus technology

Adenovirus vaccine technology has been in existence for some time. Adenoviruses in their natural form cause diseases ranging from the common cold to pink eye. Their ability to efficiently invade human cells makes them an ideal vector to shuttle genetic material into a cell.

In order to make an adenovirus a useful vector for a vaccine, it must first be modified such that the vector itself cannot cause illness. This would be an obvious downside to any vaccine. Johnson & Johnson used the vaccine vector Adenovirus 26 (AD26), which has a key gene called E1 deleted from its genome. Without the E1 gene, AD26 is still able to gain access into human cells, but is incapable of replicating. As such, AD26 is incapable of creating an infection within the human body.

DNA

The DNA component of Johnson & Johnson’s vaccine provides the human body the blueprint to generate copies of specific coronavirus antigens that elicit an immune response.

DNA sequences obtained from the initial outbreak of the pandemic in Wuhan, China, were used to isolate the sequence for the spike antigen. The code for specific antigens is publicly available. The DNA sequence for the SARS-CoV-2 spike protein is then cloned into a loop of DNA called a plasmid. Just upstream of the spike sequence, a promoter region obtained from cytomegalovirus (CMV) is spliced in, which enhances the transcription of, and ultimately the creation of, spike antigens.

There is no part of the of the Johnson & Johnson vaccine that is capable of causing infection or altering the host DNA of humans.

Additional ingredients

Beyond the viral vector and cloned DNA in this vaccine, there are some ingredients used to control the aqueous environment that the vaccine is delivered in. These ingredients preserve the stability and viability of the vaccine. These include:

  • Citrate: Used to control pH, this compound is essentially the same as citric acid found in many foods.
  • Hydroxypropyl — beta — cyclodextrin: A large cyclic chain of sugarlike molecules that aids in making other compounds more soluble in water.
  • Ethanol: Common drinking alcohol. Used in concentrations that are many magnitudes below what would affect the human body.
  • Polysorbate 80: A polymer of both hydrophilic and hydrophobic compounds. Used commonly in food as an emulsifier. Used in this application to increase the solubility and stability of the virus particles in solution.
  • NaCl: Laboratory-grade table salt. Used to control the aqueous environment.

While the ingredients in this list involve several lengthy chemical names, they are all commonly used in food and medicine.

Some of the ingredients outside of the adenovirus particles themselves serve as immune reaction enhancers — called adjuvants — that increase the speed and magnitude of the immune response. Several vaccine adjuvants have come under fire in the past decade, but most are considered to be safe for use in this application.

With just one shot, the AD26.CoV.S vaccine confers 85% protection against Covid-19. While this may seem to fall short of its competitors put out by Pfizer and Moderna, the Johnson & Johnson vaccine does come with some advantages.

Requiring only one dose of the vaccine significantly decreases the burden on public health. Requiring a second, delayed dose — as is the case with the vaccines from Pfizer and Moderna — increases the likelihood that people may not be able to complete the two-dose series, and more cost and time are required to host vaccine clinics twice instead of once.

With the level of protection offered by this vaccine, along with its protection against severe Covid-19 cases, the Johnson & Johnson vaccine appears to be a critically important part of the Covid-19 vaccine program. With Covid-19 variants beginning to gain a foothold in the United States, a rapid and efficient vaccine program is at the core of the effort to slow the ongoing spread of this virus.

Medical student, molecular biologist and educator. I write about science and medicine.

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