[jupp0r]

> R0 is not a constant inherent to a virus strain. It's a contextual number, determined by population and behavior, population immunity and other factors.

From Wikipedia: In epidemiology, the basic reproduction number, or basic reproductive number (sometimes called basic reproduction ratio or basic reproductive rate), denoted {\displaystyle R_{0}}R_{0} (pronounced R nought or R zero),[20] of an infection can be thought of as the expected number of cases directly generated by one case in a population where all individuals are susceptible to infection.

https://en.wikipedia.org/wiki/Basic_reproduction_number

[whoisburbansky]

The next paragraph calls out that R0 is not a biological constant specific to a pathogen as it is affected by environment and behavior.

[watwut]

> can be thought of as the expected number of cases directly generated by one case in a population where all individuals are susceptible to infection

Yeah, and that is contextual number, determined by population behavior and other factors.

Yes, population immunity should not be on that list, but the population behavior, weatcher and what not are still influencing it a lot.

[timr]

Population immunity has to be on the list: if the population has some level of immunity, it affects the observed R0. And we can't really measure immunity, other than in very crude ways (i.e. antibody tests for specific epitopes), so we can't control for it.

This isn't a political statement of any sort.

[timr]

You can think of it that way, but we never know, in practice, what level of actual immunity exists in a population.

In any case, it's not relevant to my point: R0 is a contextual number, always defined by empirical data. It's not a fixed feature of the virus.

[jacquesm]

Exactly. OP is simply wrong about this.