Viruses can mutate. As a host’s body starts to fight the virus, it adapts to changes to its environment, such as changing its surface proteins. Mutated viruses bring new and sometimes more severe symptoms. If the coronavirus mutated to withstand the human body’s efforts to get rid of it, then herd immunity would not be effective.
The chances of the coronavirus mutating are slim. For a virus to evolve, there would need to be several mutations that give the virus an overall environmental advantage. Therefore, there is no need to worry about the effectiveness of herd immunity.
[P1] Viruses can mutate to adapt to its environment. [P2] Mutated viruses have more harmful symptoms that could harm a human host more. [P3] Herd immunity would be ineffective with a mutated virus.
Rejecting the premises
[Rejecting P1] Viruses rarely have enough mutations to evolve.