The upper respiratory tract mucosal tissues are the places most respiratory viruses colonize first upon subject exposure. Intranasal vaccines can trigger mucosal immunity, especially secretory IgA antibodies, right at the site of infection. That’s something injected vaccines usually can’t do well.
Even if an injectable vaccine is able to prevent severe disease from those kinds of viruses, it is not completely "sterilizing" as the virus will still replicate on those mucosas and will be able to be spread even if in a less virulent fashion. Intranasal vaccines have the potential to stop those viruses before they have a chance to take hold.
The nervous system damage like that is certainly a big concern. Especially with the adjacency of the mucosal tissues of the sinuses, etc, to the central nervous system proper. And then there's the problem that intramuscular sars-cov-2 vaccination has basically zero measurable effect on long-covid syndrome(s). I really just wanted my entire body to be protected before being infected and the viral load as low as possible during infection.
>folks making their own intranasal vaccines with research peptides
I wish the RaDVaC were still available, but around the time of sars-cov-2 delta(?) they were no longer able manufacture the proteins needed for their intranasal protein vaccination (they tried but they could not produce it; a common problem with full protein vaccines). It hasn't been an option for quite a while.
The only real option would be a medical tourism trip to India to get their iNCOVACC intranasal sars-cov-2 vaccine but I do not think I have the money or ability to successfully navigate a foreign medical system.
Even if an injectable vaccine is able to prevent severe disease from those kinds of viruses, it is not completely "sterilizing" as the virus will still replicate on those mucosas and will be able to be spread even if in a less virulent fashion. Intranasal vaccines have the potential to stop those viruses before they have a chance to take hold.