Herd immunity isn't about zero transmission, it's about greatly reducing the chances for transmission.
If only 1 in 100,000 people don't have immunity, then the chance of an infected person passing it on to somebody who isn't yet immune, is a lot less than where only 1 in 10 doesn't.
From your link.
Quote:
What is herd immunity?
When most of a population is immune to an infectious disease, this provides indirect protection—or herd immunity (also called herd protection)—to those who are not immune to the disease.
For example, if 80% of a population is immune to a virus, four out of every five people who encounter someone with the disease won’t get sick (and won’t spread the disease any further). In this way, the spread of infectious diseases is kept under control. Depending how contagious an infection is, usually 50% to 90% of a population needs immunity to achieve herd immunity.
How have we achieved herd immunity for other infectious diseases?
Measles, mumps, polio, and chickenpox are examples of infectious diseases that were once very common but are now rare in the U.S. because vaccines helped to establish herd immunity. We sometimes see outbreaks of vaccine-preventable diseases in communities with lower vaccine coverage because they don’t have herd protection. (The 2019 measles outbreak at Disneyland is an example.)
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The outbreaks arise from those who
don't have herd protection.