Because an uptick in cases always has resulted in an uptick in hospitalizations and death.
Maybe you think things have changed (and indeed: I think vaccinations have changed the pattern of cases -> hospitalizations -> death). But ultimately: cases give us a glimpse of what is to come 3 or 4 weeks earlier.
And lo-and-behold, the Florida hospitalization counts are now kicking up dramatically. Good thing we got the news out weeks ago about Delta, so that public opinion can start changing (and now people are beginning to get vaccinated, which should lessen the number of hospitalizations).
Similarly: UK hospitalizations are in fact dropping now!! (coinciding with the drop in case counts 3 or 4 weeks earlier). So even in highly vaccinated countries like UK, case# remains our best predictor for hospitalization counts.
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USA is too late however: we let up on our vaccinations and this surge is going to catch a lot of us by surprise. Hospitals are filling up again.
The vaccinations are coming in too late to stop this current surge (July / August timeframe). But the vaccinations will help us prevent a winter surge.