Really All? Please stop posting that herd immunity does not exist. It is a scientific fact. I think what you are arguing is the you don't believe herd immunity can be achieved without a vaccine. But exposure to the virus and a vaccine is what creates herd immunity and causes the virus to dissipate.
Nobody is disputing that herd immunity is a concept. It's based on reducing the number of interactions between infected people and people that are able to be infected.
Here's a good visualization
In the context of COVID, and hence assumed in this thread, the discussion has been if the number of people that cannot be infected can be achieved through natural infection instead of with a vaccine. Along with some details on how large that number needs to be, probably more than flu but less than measles. Combined with questions on how many are already infected, assuming the reported number is orders of magnitude to low. Plus mixing in a little bit of if being infected actually turns someone into "cannot be infected" and for how long.
In the visualization, if all the green dots already had COVID and recovered instead of getting a vaccine.
But exposure to the virus and a vaccine is what creates herd immunity and causes the virus to dissipate.
When someone says, and this is what's assumed in this thread, that the plan to deal with COVID is "natural herd immunity" it's being interpreted as "enough people are infected with COVID that then become no longer able to be infected again as a percentage of the population that transmission to new cases is reduced to a low number.
That's the scenario that people are saying is not possible.
Or, rather, the death toll to get there is unacceptable. Combined with that it's not a final state. As the population turns over, the "no longer able to be infected" percentage will drop and new cases will rise until it's lowered again. A repetitive cycle of deaths, mostly in kids.
A vaccine solves this problem in two ways. First, it lets us create a huge number of "no longer able to be infected". Second it does this with a very low risk. All those decimal points in the safety percentage are important when the doses given is such a huge number.
The math isn't hard:
Population * Immune % = Number Immune to achieve Required herd immunity.
Getting there naturally through infection instead of vaccine means:
Population * Immune % = Number Infected to get natural herd immunity.
Now do the death toll.
Number Infected * COVID Death% = Deaths.
Combined it's:
Population * Immune % * COVID Death% = Deaths to achieve natural herd immunity.
We can debate the different scenarios:
328,239,523 * 60% * 2.59% = 5,102,205 deaths.
328,239,523 * 20% * 0.26% = 170,685 deaths.
So, for everyone that's all about how natural herd immunity will get us there, what's your guess at two percentages and how many deaths are acceptable to you?