Unless the 10% of folks not vaxxed over 50 are because they are too frail for the vaccine. That is something Alex Berenson surmised in Israel. BTW, not Delta specific, but I wanted to see how CFR was changing over time as we would expect it to be going down significantly (vax meant to prevent severe disease). You can look at that for the US (slice and dice by region/state/county) at the following link (4th tab). Interestingly the general pattern is a dip in the spring & a rebound in summer, similar to your graph. https://public.tableau.com/views/CovidbyClimate/CountyVaxTimeSeries?:language=en-US&:display_count=n&:origin=viz_share_link