BREAKING: Literally None of the 30 Youths who contracted Whooping Cough in Los Angeles county were Not Vaccinated

No Upper Bound wrote:

Here we had almost 99% vaxxers (1582/1600), and yet the herd was not protected from itself.

First some history:

The concept of “herd immunity” first materialized in the 1930s, when Johns Hopkins University’s Arthur Hedrich discovered that, after 55% of Baltimore’s population acquired measles (and thus immunity to measles), the rest of the population, or “herd,” became protected. This concept provides today’s rationale for insisting that everyone be vaccinated.

In November 1966, in announcing a mass vaccination program for measles that would exceed the 55% level reached in Baltimore, the U.S. Public Health Service confidently announced that “Effective use of these vaccines during the coming winter and spring should insure the eradication of measles from the United States in 1967.”

When measles failed to be eradicated, public health experts decided that a 70% or 75% vaccination rate would secure herd immunity. When that proved wrong, the magic number rose to 80%, 83%, 85%, and then it became 90%, according to a 2001 Health Services Research report. Later health experts commonly cited 95%.

But that too was insufficient — measles outbreaks occur even when the vaccinated population exceeds 95%, leading some to say a 98% or 99% vaccination rate is needed to protect the remaining 1% or 2% of the herd. But even that may fall short, since outbreaks occur in fully vaccinated populations.

“The target would be to have 100% of the population vaccinated,” Dr. Gregory Taylor of the Public Health Agency of Canada recently told CBC, voicing an increasingly common perspective among public health professionals. (At that point, the balance of the herd that would be "protected" through mass vaccination would be in fact 0.)

But even vaccinating 100% of the population wouldn’t be enough, say scientists at the Mayo Clinic’s Vaccine Research Group, because the measles vaccine is a dud with some people, offering no protection at all, and its effectiveness wanes with others, even if they get boosters.

In fact, herd immunity — so elusive today — fully existed prior to the vaccine’s introduction. Virtually 100% of the population then contracted measles, typically as children, giving everyone lifelong immunity — and future mothers the means to protect their offspring. In mass vaccinating us, scientists of the 1960s didn’t realize that infecting us with the measles vaccine — a weak version of the natural measles virus — would give us a weak version of the defenses our bodies develop to the real thing.

The measles vaccine works as planned with only 25% of the population. The Public Health Service considered measles generally benign in the pre-vaccine era. Complications are infrequent and, with adequate medical care, fatality is rare. Up to half of today’s measles cases involve adults. Unlike childhood measles, adult measles is dangerous: 25% of cases require hospitalization.

As with any garbage in-garbage out type of theory, the expectations of the herd-immunity theory are bound to fail in the real world.