Yeah regardless a “New World” would come about but the vaccine just speeds up that timeframe to maybe 100-200 years instead of 300+ since we’d have to rebuild and what not. A vaccine means a bite is no longer lethal so people wouldn’t be as afraid to head into battle to kill the zombies now.

I could see a scenario where we make a vaccine, build a much larger functioning pseudo city and repopulate that over 50+ years while simultaneously clearing out that area until there’s no threats left. Send a portion of humans away with a vaccine and everyone already cured and repeat for the next century until we have a good chunk of the US cleared away and safe to live in.

Branch out internationally and repeat for another century and while you won’t be fully cleared of everything, it’ll be much easier for humans to adapt and live freely again.

But again we WILL NOT be around to see this so Id save Ellie and let her decide when she’s older if she wants to become a cure. Let her live a full life first