The new COVID-19 vaccines from Johnson and Johnson (JNJ) and AstraZeneca utilize an adenovirus-vector to prevent the SARS-CoV-2 virus that causes COVID-19. Of course, this being a new vaccine technology, like the mRNA vaccines used by Pfizer and Moderna, we will be hearing all kinds of false claims about the new adenovirus vaccine.
So, this article will just try to explain what an adenovirus is, how it works in vaccines, and why it is safe. There’s going to be a lot of science here, so I’ll do my best to link you to good articles that explain some of it.
The anti-vaccine squad used an ignorance of basic cell biology to make all kinds of odd claims about the mRNA vaccines such as claiming that it would change the DNA of the vaccine recipient. It can’t.
What is an adenovirus?
Adenoviruses are a group of viruses in the taxonomic family Adenoviridae. They contain a double-stranded DNA genome. These viruses have a wide range of vertebrate hosts, including some species of birds, frogs, sturgeon, cattle, and mammals including humans.
There are more than 50 distinct adenovirus serotypes known to infect humans. These viruses cause a wide range of illnesses from mild respiratory infections in children, known as the common cold, to serious, life-threatening diseases in people with weakened immune systems.
Adenoviruses are a popular tool for gene therapy. This is due to their ability to affect both replicating and non-replicating cells and accommodate larger genes to transfer. Of course, this will send up warning flags to anti-vaxxers, because they think all vaccines mess up your DNA.
However, in vaccines, adenovirus vectors have been studied because they can code for proteins without integrating into the host cell genome, similar to mRNA vaccines.
What are the adenovirus vaccines?
The JNJ and AstraZeneca COVID-19 adenovirus vaccines are quite different than the Pfizer and Moderna mRNA vaccines. All of these vaccines induce an adaptive immune memory response by creating the S-protein of the SARS-CoV-2 virus that causes COVID-19.
The JNJ COVID-19 vaccine, known as the JNJ-78436735, utilizes a recombined adenovirus vector, human Ad26.COV2.S., which expresses the S-subunit of the SARS-CoV-2 virus to induce an immune response. The AstraZeneca adenovirus vaccine uses a recombined chimpanzee adenovirus vector, ChAdOx1, There are no functional differences between the chimpanzee and human adenovirus vectors, it’s just how the research was done on trying to develop these vaccines.
Adenovirus-based vaccines are not new – they have been investigated for several decades. In fact, JNJ received approval for an Ebola adenovirus vaccine in July 2020, so the technology did not appear suddenly just for COVID-19. However, like the mRNA vaccines, these adenovirus vaccines can be quickly developed to deliver the most important antigen on the SARS-CoV-2 virus, which is the S-protein.
Once the adenovirus-vector COVID-19 vaccines are injected into the arm, the adenoviruses enter cells and moves to the nucleus, where the cell’s genes (DNA) are located. Basically, the adenovirus vector “carries” the genes for the S-subunit to the cell which will reproduce the protein, then inducing the immune response.
The adenovirus then injects its DNA into the nucleus. The adenovirus is engineered so it can’t make copies of itself, but the gene for the coronavirus spike protein can be read by the cell and copied into a molecule called messenger RNA, or mRNA.
At this point, these vaccines work in a manner similar to the mRNA vaccine technology.
Normally, during the process called transcription, RNA polymerase makes a copy of a gene from its DNA to a corresponding mRNA fragment whenever required by the cell. In other words, the mRNA sequences in the cell usually correspond directly to the DNA sequences in our genes. These mRNA sequences “carry” that genetic message to a ribosome for translation, where tRNA triplets, which code for one amino acid, attach to the appropriate mRNA triplet, adding one amino acid to the protein chain.
As in DNA, genetic information in mRNA is contained in the sequence of nucleotides, which are arranged into codons consisting of three ribonucleotides each. Each codon codes for a specific amino acid, except the stop codons, which terminate protein synthesis.
Like with mRNA vaccines, the adenovirus does not change the genetic code of any of the 50 trillion cells that are in a human. All that happens is that the adenovirus injects DNA that is coded for the S-protein and the cell produces mRNA from that DNA that then causes the ribosomes to produce the S-protein.
Those S-proteins migrate to the surface of the cell which is then recognized by the immune system as foreign invaders. The immune system then remembers those antigens – when the actual SARS-CoV-2 virus attacks, the immune system is ready to attack.
There are several good reasons why JNJ and AstraZeneca (along with other vaccines that will never be available in the US, Europe, and other developed countries, such as Sputnik V) decided to use adenovirus technology for their vaccines:
- For most people, the adenovirus is a mild one. Even if some unicorn-like situation arose, the virus will not cause much more than an inconvenience to most people.
- It also is one that we have a lot of experience making even milder.
- The adenovirus vaccines also have an important advantage over the mRNA vaccines – the adenovirus itself provokes the immune system to activate immune cells that are nearby. This leads to the immune system reacting more strongly to the spike proteins.
- Only one shot is required as opposed to two that are required for the mRNA vaccines (although both Pfizer and Moderna are examining whether they can recommend just one shot eventually).
- The adenovirus-based vaccines are much less fragile than mRNA vaccines because they are based on DNA which is more rugged than RNA. That’s why the recommended storage methods for these vaccines are less stringent than the mRNA vaccines.
Pre-debunking the upcoming myths
So, let me make this blunt:
- The adenovirus vaccines will not change your DNA in any way. Even though adenovirus vectors are used for gene therapy, they use different serotypes of adenovirus for those purposes, and these vaccines utilize a virus that cannot replicate and cannot affect your DNA.
- These vaccines will not cause infection by adenovirus, because they cannot replicate.
- Even if there was some mistake in the lab, the adenovirus serotype used will only cause mild symptoms.
- Although the clinical trials for the AstraZeneca and JNJ COVID-19 vaccines showed somewhat lower overall effectiveness, it’s really bad science to compare one clinical trial, which has different protocols and disease settings, to another one. Both of these adenovirus vaccines prevent mortality and serious COVID-19 outcomes.
- These vaccines are not “rushed” new technology – they have been studied for over 50 years, and there are vaccines based on this technology already approved by various regulatory agencies.
- And not to be repetitively repetitive, this vaccine will not change your DNA.
As I wrote before, these four vaccines from AstraZeneca, JNJ, Moderna, and Pfizer are all very safe and extremely effective. The one that is available is the one you should get.
- Chawla T, Khanna N, Swaminathan S. Adenovirus-vectored vaccines. Expert Opin Ther Pat. 2008 Mar;18(3):293-307. doi: 10.1517/135437188.8.131.523. PMID: 20144086.
- Lee CS, Bishop ES, Zhang R, Yu X, Farina EM, Yan S, Zhao C, Zheng Z, Shu Y, Wu X, Lei J, Li Y, Zhang W, Yang C, Wu K, Wu Y, Ho S, Athiviraham A, Lee MJ, Wolf JM, Reid RR, He TC. Adenovirus-Mediated Gene Delivery: Potential Applications for Gene and Cell-Based Therapies in the New Era of Personalized Medicine. Genes Dis. 2017 Jun;4(2):43-63. doi: 10.1016/j.gendis.2017.04.001. Epub 2017 Apr 27. PMID: 28944281; PMCID: PMC5609467.
- Thacker EE, Nakayama M, Smith BF, Bird RC, Muminova Z, Strong TV, Timares L, Korokhov N, O’Neill AM, de Gruijl TD, Glasgow JN, Tani K, Curiel DT. A genetically engineered adenovirus vector targeted to CD40 mediates transduction of canine dendritic cells and promotes antigen-specific immune responses in vivo. Vaccine. 2009 Nov 23;27(50):7116-24. doi: 10.1016/j.vaccine.2009.09.055. Epub 2009 Sep 26. PMID: 19786146; PMCID: PMC2784276.
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