tryptaminev , 6 months ago

Is it 97% on the basis that herd immunization makes your exposure unlikely, so that you’d at best be exposed to a single person that could contract it to you?

Or is it 97% on the basis that you are submerged in an atmosphere full of people sick from measles?

WHO information on these numbers

So either it refers to a clinical trial with a defined exposure, or it referes to empircal data that is based on the conditions in the real world, which critically includes the herd immunity.

Herd immunity is a critical factor and it works exponentially. E.g. from 100% to 95% is less of an issue than from 95% to 90% The critical point for measles is at around 92% to prevent exponential infections. This included the risk for people who are vaccinated

https://upload.wikimedia.org/wikipedia/commons/thumb/0/0f/Herd_immunity_threshold_vs_r0.svg/768px-Herd_immunity_threshold_vs_r0.svg.png

Measles are among the most contagious diseases. To interpret the graph. Because of the high R rate w.o. immunization, you need 92% immunization rates to have one measle case cause another measle case, e.g. reproduction = 1. You go below and it goes exponential.

Wikipedia - Herd immunity