There are few SARS-Cov-2 vaccines that use adenovirus vectors as vehicles (human's Ad5, Ad26, chimps' ChAdOx1, probably something else). A side effect of such a vaccine is that an inoculated organism develops an immunity against the vector itself.
This (probably) means that for some time, while the immunity is effective, inoculation with a vaccine using the same serotype of adenovirus will not be effective.
Also, as some types of genetic therapy could also use the same adenovirus-based technique, an inoculation-induced immunity would (probably) also negate (or lessen) the effect of such therapies.
In this light, it seems that it is important to know how long such an immunity lasts. (Please note that I'm talking about the immunity to the adenovirus, not SARS-Cov-2). I tried to find 'how long does it last?'. I found something like 'adenovirus immunity does not last long', but nothing concrete. Also, there are articles like this https://pubmed.ncbi.nlm.nih.gov/30266488/ that study the matter in... mice... but I'd like to get an answer applicable to humans.
Are there any estimates?
A later addendum for newbies like me: adeno-associated viruses (AAV) is not same thing as adenoviruses (AdV). All the 'viral' vaccines against SARS Cov-2 that I know are using AdV, while (potential) genetic therapies (about which I heard) usually use AAV (but googling reveals that AdV can also be an option). The point is that, when trying to understand whether a vaccine can interfere with a potential genetic treatment, one needs to keep in mind that AAV is not AdV!
But the original question still remains open.