I haven't read those SAGE predictions and I should do I suppose, but I take it that they take fully into account how widespread vaccinations will have been in the UK, by the end of summer?
So even if vaccinated people still spread the virus (and how much is
confidently known yet about that?) should at least mean that significantly fewer people might go into hospital, and lower death rates. What with so many of the elderly (most vulnerable) having been jabbed, just to give an example.
And no, I'm
not saying "Rely on the vaccine and everything will be fine tra la!", just urging caution against ultra-pessimism
at this stage.
Continue to be careful;, but don't
assume the worst, in short. I'm guessing just as much as you, but still.