what you call "herd immunity" is merely letting people die and then go "we have herd immunity" as part of your survivor bias
only solution that works most of the time, regardless of pathogen (including covid): air filtration (respirators and/or whole room)
After vaccination or a passed infection the immune response is there. When a sufficient immune resopnse from a large enough portion if the population is enough to lower the critical cases below some threshold, we call that type of immunity herd immunity.
It's not binary, but a useful concept nonetheless, and one that some people devote their professional lives to. It can be observed every flu season.
Regardless, herd immunity was not a serious possibility at any point (given the high Rº and lack of a vaccine that could prevent transmission), which, considering this was known very early on makes your question, again, a good one not a rhetorical one, despite your intent.
Finally, regardless of herd immunity, at risk individuals would still require vaccination, which makes the herd immunity as a goal, again, irrelevant, which is where I started. It's a nice by-product.
Though, to be fair, my whole family caught a "virus" during 2nd phase except my father but we didn't go to hospital and just bed rest for 2-3 days. My family really were skeptical of vaccine but personally I don't mind vaccines and would prefer it.
Think of the children ... :-)
...or getting infected, of course.
[0] https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
The current breed of mRNA vaccines targets the spike protein, and the TRIM21 gene. Some of them also attack the S protein directly.
All of them work to boost various antibodies. The "targets" are in addition. By targeting the spike protein, the attack hits the RNA of the virus, not just the protein. The entire cellular structure of the virus breaks down. The same with TRIM21 targets.
The bodies natural defences never targeted the spike protein, and instead focuses on the N-layer, not "all parts of the virus". These natural defences rarely manage to cause the viral cell to decay, they tend to work by slowing reproduction instead.