Natural immunity isn't as strong as what the vaccine gives you and it doesn't last as long as what the vaccine does. You complain about it being coercive to try and force you to have a jab but don't like the idea of business owners deciding who works from them. If you don't want the jab don't have it. If a business owner doesn't want staff or customers who haven't had the jab they don't have to because it's their choice just like it's yours. You are a third as likely to pass on covid or catch it if you've been jabbed.
From what I've read there isn't a definitive answer for this.
If you read science articles then the jury is still out, words like 'may' and 'might' are used.
The NHS and CDC say you should still get the vaccine, but then they would say that, other scientists say different as is normal in any other medical situation.
With both natural immunity and vaccination the odds of future infection and level of illness are both dependent on age, comorbitities ect
Surely if vaccines were the only way to secure longer immunity, then proof of previous covid infection wouldn't be used on the domestic passports
If a business owner does try playing that card then they need to tread carefully as vaccines aren't mandated and legally they might be open to being sued