As I understand it, the risk is not to do with the adenovirus but with the use of PEG (polyethylene glycol) or similar analogues, to make the active ingredient last longer, which may cause an allergic reaction[1] to sensitized people. The AZ vaccine does not use PEG (nor J&J, Novovax IIRC).

The complication with the adenovirus carrier is that you immune system may attack the carrier so effectively that you don't get enough exposure to the coronavirus protein that it is carrying, and hence don't develop a strong enough immune response to it. This causes problems determining how people will respond to varied treatment schedules (delay of the booster shot, mixing of vaccines, etc).[2][3]

The mRNA vaccines do not get your cells to 'appear infected'. See https://www.youtube.com/watch?v=LcTEmHlvY10

[1] https://www.sciencemag.org/news/2020/12/suspicions-grow-nano... [2] https://www.sciencedirect.com/science/article/pii/S152500160... [3] https://blogs.sciencemag.org/pipeline/archives/2020/12/02/ta...

Your video specifically mentions triggering a 'cytotoxic T-cell' - that's a cell that kills virus-infected cells. What's more, it doesn't explicitly state that all the bodily cells that receive the foreign mRNA survive.

I'm pretty sure they're attacked & destroyed by the immune system for their emission of foreign proteins - that is, they "appear infected". And, some time after the mRNA was introduced – days? weeks? – it's all used up, because unlike a full viral vector, it doesn't code for more invasive genetic material, only proteins. And, the cells it hijacked are in some combination, destroyed by the immune system or revert back to normal, non-threatening operation.

If you have a more specific reference that denies the mRNA-altered cells are attacked-as-if-infected, I'd appreciate seeing it. But that video doesn't make that claim, and in fat the reference to 'cytotoxic T-cells' implies the opposite.

(Also, as the sibling response elaborates, the problems with Adenovirus-vectors are not limited to PEG reactions.)

There are a number of direct risks related to the Adenovirus itself. Multiple adenovirus vaccine programs have been scrapped over the years because of these issues:

https://cen.acs.org/pharmaceuticals/vaccines/Adenoviral-vect...

For example, famously, one Ad-based HIV vaccine was found to increase the chances of getting HIV. People still theorize that it might be due to the vector itself:

https://www.thelancet.com/journals/lancet/article/PIIS0140-6...

(that said, these platforms are certainly better validated than the mRNA-based vaccines. There's an approved rabies virus vaccine based on adenovirus.)

Yes other complications are possible, I had thought from the wording it was a concern about allergic reactions.