This is an interesting article on a possible approach to long-standing COVID-19 immunity here.
One of the problems with other approaches is that other coronavirus immunity is not typically long-lasting, and fades. Thus, even herd immunity may not give us long-term protection, and standard vaccine approaches might need to be repeated frequently.
This approach, if feasible, would be a game changer. And its written by someone who actually knows what they’re talking about.