IMO, this would be the wrong conclusion. I had a lightbulb moment when scrolling through Twitter today, and it is related to your conclusion here. Throughout this pandemic we have been inundated with numbers and percentages, and we can recall many of them and pepper our posts with them. But they are usually based on the ORIGINAL virus, or at least the variant that came through Italy and dominated cases until Alpha (UK) and now we're transitioning to Delta (India). Most of these numbers are no longer valid, because the virus they were for has been replaced with a new virus with different numbers. Each iteration has been small, but as time passes and new variants replace old ones the change from the original can become wider, and at some point they will be effectively meaningless. Unvaccinated people are weighing their risk that if they get sick, they are young, healthy, but the sickness they are envisioning is likely to be a picture of what the original virus looked like; not the one they are risking. Which at this point is Delta.
Which brings me to the number of references from my EpiTwitter who kept referring to Delta as "nasty." These are people that throughout have been telling people to calm down every time variant talk came up, because it meant things were different, not that things were necessarily worse. They are all operating that what is out there now is "worse" and thankfully those that are vaccinated are protected. But as
@seascape and others look at the numbers that get posted after summer holiday gatherings, and certainly when we get back into the winter period, we should be aware that the rates of hospitalization, the more severe versions of the "mild / doesn't require hospitalization", and the affected ages will look different than they did last year. It will be a smaller number of people, but they will be experiencing worse outcomes than the people that got sick last year. And we'll have to see what happens with long-Covid for this bunch. Those of you who live in areas with low vax rates are likely going to be seeing different things in your communities than those of us who have reached 70%.
The time period of this study, is undoubtedly how well previous infection does against Alpha. We also know that reinfection against Brazil's variant was greater than reinfection against Alpha. What reinfection for Delta is, I haven't looked for. We can not assume that since Alpha held up against reinfection that all future variants will as well. Every iteration changes the game, and we can only count on our defenses being adequate as long as the opponent doesn't upgrade their offense. Any risk calculation should be based on what Delta does to people.