Herd immunity, I believe is a rather complicated phenomenon. And the experts are reluctant to give credit to it, where the virus cases decreased over a period of time.
Here’s an assumption of a phenomenon, something similar to herd immunity, that was observed in a journey by road covering three Indian states.
It started from one state where the mask was seen the norm, though many if not most were worn below the nose.
Entering the next state, it was difficult to find people with masks. The story my brother told me alludes to this.
His helper in Kerala from the neighbouring state, went home and returned saying that there’s no Covid in his home town as no one was wearing a mask.
Continuing the interstate journey, we entered Kerala. It’s complete, all with masks, without exception and there’s even masked police primarily enforcing the mask rule to the letter.
Herd immunity then! Well yes, the two states with much larger population are reporting decreasing new virus cases and in fact at a fraction of Kerala’s, where even the positivity rate is perhaps the highest.
Will herd immunity then is like the virus entering a healthy body, get attacked by the strong immunity, get weakened and enter another healthy body, to be weakened further and so on and on to be ineffective even inside a weak body.
Of course, we can’t abandon the good acclaimed practices and it’s strict enforcement. That’s why it’s only a view.