‘For an infectious disease to be classed in the endemic phase, the rate of infections has to more or less stabilize across years (though occasional increases, say, in the winter, are expected).
“A disease is endemic if the reproductive number is stably at one. That means one infected person, on average, infects one other person,” explained Boston University epidemiologist Eleanor Murray.
“Right now, we are nowhere near that. Each person who’s infected is infecting more than one person.” That’s largely due to the hyper-contagious delta variant and the fact that most of the global population doesn’t yet have immunity — whether through vaccination or infection — so susceptibility is still high.
(For a while, there had been hope that the arrival of vaccines would mean we could reach herd immunity — that is, when enough of a population has gained immunity to confer protection to everyone. But those hopes have been dashed as we’ve failed to vaccinate enough people and more contagious variants have circulated widely.)
But getting the virus’s reproductive number down to one is just “the bare minimum” for earning the endemic classification, Murray said. There are other factors that come into play, too — and assessing these factors is a more subjective business…’
— via Vox