So, my IANAD understanding is that a harmless adenovirus is tweaked to produce surface protein found on the surface of the COVID-19 virus. This way, as your immune system learns to identify and eliminate the adenovirus, it also learns to identify and eliminate anything with the COVID-19 surface protein.
This makes me wonder if there is a brief period when you are building immunity-- that “feeling unwell” period, that comes about 8 hours in, and ends about 30 hours in, the adenovirus is multiplying.
If that is the case, are you shedding virus, and can someone catch the altered virus from you? In other words, could someone actually “catch” and inoculation by becoming infected by someone else’s adenovirus?
I’m thinking probably not, because the developers of the vaccine probably took this into account. On the other hand, I remember reading that this was something possible with the Sabin polio vaccine.
The Sabin vaccine was not an adenovirus vaccine-- it was a live but attenuated polio vaccine. Still, in both cases, you have a live vaccine that has been altered.
Am I just delirious, or is this actually possible?
Tried Googling and couldn’t find anything. Emailed my cousins who are physicians and a virologist, but not heard back. The one who is a virologist lives in Texas, and has a toddler and an infant, so she probably doesn’t have time to answer idle questions.
First of all, the adenovirus vector does not produce the SARS-CoV-2 spike protein itself. It contains the gene (the DNA sequence) for the spike protein. After the adenovirus vector enters your cell, your cell’s own machinery produces the protein encoded in the gene. In this respect it is similar to the mRNA vaccines, it induces your own cells to make the spike protein. The difference is that adenovirus is made of DNA, like your own genome, so your cell first transcribes the adenovirus DNA to mRNA, then translates the mRNA to protein.
Second, you are never infected with adenovirus. The injected adenovirus vector acts like a fully-functional adenovirus virion at first, doing what adenovirus normally does to gain entry to your cells. But once inside your cell, it cannot complete its “life cycle”, because key viral replication genes have been deleted. Instead of instructing your cell to make lots more adenovirus, all it can do is instruct your cell to make spike protein.
So no - you are never infected, and the adenovirus vector cannot be transmitted to somebody else.
Here’s a review of adenovirus vectors from 2018. Some of it gets quite technical, but there are some straightforward introductory sections on the principles involved, and some nice diagrams.
This is exactly right. The modified adenovirus is just a delivery system for the gene sequence of the SARS-CoV-2 S-protein but it does replicate itself, nor is it capable of being contagious to others. The adenovirus used for the Janssen/J&J vaccine (Ad26) is a human-adapted adenovirus which produces mild respiratory infection and make act as an adjuvant, essentially priming the immune system to react to the S-protein, hence the effectiveness of a single dose vaccination. Adenoviruses in general have been used for numerous gene therapies and certain cancer treatments because of their broad and mutable tissue tropism (e.g. the types of cells they can infect) and the mild symptoms they produce.
You can summarize it this way. The functional aspects of the natural adenovirus that are retained are:
(1) It’s good at getting into your cells.
(2) It is a good adjuvant - your body recognizes it as something that should not be there, and puts the immune system on high alert, just what you want for a vaccine.
(3) Once inside your cell, it’s good at making your cell do what it wants.
But the instructions it contains are completely modified. Instead of “make lots more adenovirus”, it is “make spike protein”.
Well, darn. I was hoping to sneak into an anti-vax coffee klatch, and breath all over the half & half.
No, really. I didn’t think it would be transmitted through the air, but I thought it might be through, umm, you know, not enough hand-washing. But I guess the Sabin vaccine was oral, not injected.
Maybe someone will come up with an oral COVID vaccine in the near future.
Albeit, if the articles I’m reading are accurate, all but the most hardcore anti-vaxxers are starting to get COVID shots. A lot of initial hesitance is falling like dominoes. Nothing like having actually experienced the disease in its “plague” form to push the fence-sitters off into our camp.
Unlikely; while SARS-CoV-2 can infect the intestinal epithelium (as evidenced by intestinal pain and gastrointestinal distress in a minority of infected people) it doesn’t seem to propagate from there very effectively if at all. An nasally inhaled vaccine is certainly a possibility, though.
I got the joke, but in reality it would be great if there were a vaccine that didn’t require intramuscular injection because of how much that would simplify logistics, especially to developing nations where medical training is rare. As for the anti-vax crowd, we often think that the solution is education but the old saw about bringing a horse to water applies there; peer pressure and being faced with the reality of being excluded from society are far more effective levers to achieve comprehensive vaccination.