Herd immunity is a scientific medical fact. Research it. It’s not a theory.
The fact is that “herd immunity” is not .... immunity. Expose the herd to the disease that they are not immunized against and those that are not immunized, get sick. There is no immunity.
From Wiki:
“... The greater the proportion of individuals in a community who are immune, the smaller the probability that those who are not immune will come into contact with an infectious individual.”
Note the term “probability” - not immunity. Research basic math probability - you will see that no immunity is provided.
see the definition of immunity:
Definition of immunity
: the quality or state of being immune especially : a condition of being able to resist a particular disease especially through preventing development of a pathogenic microorganism or by counteracting the effects of its products