Yes, there are some people that will still develop COVID infection post-vaccination. It will be interesting to see clinical characteristics of those folks in that report as well as viral variant info.
I would guess that many of them will be people for which we had no data (or limited data) on relative effectiveness compared to people in the study population. We're giving it to people with immune compromise in the hope that it will at least provide some partial protection (Cancer patients, transplant patients, HIV, people on immunosuppressive meds for auto-immune disorders, etc., etc.). There's some data emerging over the last ~1-2 weeks confirming that these folks don't develop as strong an antibody/T-cell response vs. people without those immune-compromising conditions.