[BenMcr]

Originally Posted by nomadking

Herd immunity is about reducing transmission levels. The fewer people who reach the infectious stage, the fewer can become further infected.

However we've never got herd immunity just by letting a disease spread.

https://www.jhsph.edu/covid-19/artic...h-covid19.html

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.)

For infections without a vaccine, even if many adults have developed immunity because of prior infection, the disease can still circulate among children and can still infect those with weakened immune systems. This was seen for many of the aforementioned diseases before vaccines were developed.