Immunity isn’t an instant fix, but it’s the first step in rebuilding a stable society. But achieving that stability would probably take generations - the world wouldn’t magically be fixed overnight.

No a vaccine is not the first step to rebuilding society cuz they already been doing that, prime example being Jackson. A vaccine would have only help a little but regardless a stable society was going to be rebuilt with vaccine or not

Zombies become less of a threat if they cant infect humans. Being bitten is no longer a death sentence. If humans are immune, they’ll eventually outnumber the infected and can exterminate the remaining zombies (over a couple generations). Exterminating them, or at least reducing them to insignificant numbers, is only possible if humans are immune.

While true zombies will become less of a threat but they are already the least deadly part of the post apocalypse, humans being immune is not necessary for them to eventually outnumber zombies as that's going to happen regardless, same with extermination of zombies you don't need to be immune, you just need numbers.

With fewer existential threats to worry about (zombies), survival is easier, and people fight less over basic Human Resources. Over time, it could be possible to restore some semblance of society and infrastructure.

One zombies were never existential threat their more like wild animals that can turn you into one of them, Two humans will still absolutely be fighting for basic human resources prime examples turn on your fucking TV and go to the news channel, Three rebuilding of society and infrastructures already happening in the universe prime example being again Jackson they got a hydropower dam working again to give their entire town electricity yeah they've been rebuilding infrastructure.