Lately, there has been a lot of buzz about COVID-19 vaccines, particularly regarding mRNA vaccines from Pfizer-BioNTech and Moderna (check out our post here for more information). But, what about the Janssen vaccine produced by Johnson & Johnson?
Vaccines are meant to trigger an immune response, to teach us how to fight the SARS-CoV-2 virus* (more information here). How can a vaccine teach us to fight SARS-CoV-2 without actually exposing us to the virus? The idea is to take a piece of SARS-CoV-2, one that cannot cause any harm by itself, and teach our body how to fight it. Therefore, instead of facing the deadly virus, our body only needs to learn how to identify and fight the spike – a protein on the surface of SARS-CoV-2.
Now, the question is: How do we make the cells produce the spike? The Janssen vaccine has an ingenious solution: deliver the spike DNA** into our cells using a modified adenovirus. This adenovirus has been modified so that it does not replicate and does not make people sick. Thus, the adenovirus will only be a vector*** – a transport mechanism that will allow the genetic material to enter the cells. Once the DNA is in the nucleus, the cell can produce the spike mRNA and, later on, the spike protein (check here for more information about this topic). Once the protein is produced, our immune system will learn how to recognize the spike and produce antibodies against it. In the future, because our bodies recognize the spike, they can recognize the SARS-CoV-2 virus and fight it much more effectively [1].
Using the adenovirus as the delivery method is a smart move. This modified adenovirus is deficient in replication, so it will not replicate nor make us sick. Moreover, using the adenovirus as the shuttle creates a strong immune response in our body, so our body learns about the spike quickly. It is important to note that the DNA in the adenovirus will not change our genome DNA. Even in nature, outside the lab, adenoviruses do not typically integrate their DNA with the genome of the host [2]. In other words, although the DNA goes into the nucleus, it remains outside the chromosomes as extra-chromosomal fragments. Thus, even though the Janssen vaccine includes the spike DNA, this DNA would not alter the genome in our chromosomes****.
Ideally, we hope that treatments can bring benefits without any risks. However, in reality, sometimes you must balance the known benefits versus the potential risks. There have been some reports that the Janssen vaccine could be related to the occurrence of blood clots with low platelets. Although these side effects are very rare, the risk is mainly applicable to women younger than 50 years: An adverse blood clot can happen for 7 out of 1 million vaccinated women [3]. The rate is even lower in women that are 50 years or older: In this case, the risk would be 0.9 per 1 million vaccinated women [3]. Therefore, the benefits of receiving protection against the deadly COVID-19 outweigh the risk of blood clots. That is why the CDC is recommending that the Janssen vaccination continues.
Still, it is important to remain on the lookout for possible symptoms after vaccination, so people should monitor themselves for three weeks after receiving their shot. If they develop symptoms (like easy bruising, abdominal pain, severe headaches, swollen legs, pain in the chest, or shortness of breath), they should seek prompt medical attention [3].
*Virus - it can be considered a very small and basic life form or an aggregate of molecules that is simpler than a cell. They can be found in the environment or inside living organisms. It has to infect a cell and use its machinery to multiply, since it cannot multiply by itself. Viruses consist of nucleic acids (DNA or RNA), a protein capsid that contains the nucleic acids and, sometimes, an external envelope of lipids. The flu, measles, AIDS and Covid-19, for instance, are caused by viruses.
**DNA - deoxyribonucleic acid, one of the nucleic acids found in living cells. DNA is formed by 4 nucleotides, which can be organized in different sequences and different lengths like letters are organized to form a text. In this case, the “text” formed by the sequence contains the instructions to form a whole organism. DNA is normally found as a paired double strand, in a double helix shape.
***Viral Vector - a modified viral structure that is used to deliver a molecule of interest to desired cells. The infecting and dangerous features of the virus are suppressed and it acts as a vehicle carrying a molecule that will have some specific effect in a target cell. Some vaccines and gene therapies use viral vectors.
****Chromosomes - a long DNA molecule that can be compacted into smaller and denser structures inside cells. This compacting action is made possible by the assistance of some specific proteins. Chromosomes contain all or part of the genetic material of an organism. Humans usually have 46 chromosomes per cell.
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Written by: Nicole
Edited by: María and Natasha
BioDecoded is a volunteer group committed to sharing accurate scientific information. We cannot offer any specific health advice. If you have any doubts about getting vaccinated due to previous health conditions, please speak with your healthcare professional or family physician. Your doctor can revise your medical history and advise you on the best path to follow. If you have any questions about this topic, please comment or send them to our email.
References:
Livingston, E., Malani, P. & Creech, C. The Johnson & Johnson Vaccine for COVID-19. JAMA 325, 1575 (2021). Available at: https://jamanetwork.com/journals/jama/fullarticle/2777172
Lee, C. et al. Adenovirus-mediated gene delivery: Potential applications for gene and cell-based therapies in the new era of personalized medicine. Genes & Diseases 4, 43-63 (2017). Available at: https://www.sciencedirect.com/science/article/pii/S2352304217300272
COVID-19 Vaccination. Centers for Disease Control and Prevention (2021). Available at: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/JJUpdate.html (Accessed: 23th August 2021)
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