The obvious highest category of persons to vaccinate was long-term care residents, so we should see the effects of vaccination show up in that group first. An extremely high percent of those residents have been vaccinated and the chart below suggests that there is an effect on death. You would need to look at the trend in non-LTC deaths at the same time, and, at least in Minnesota, deaths in that group are not declining as fast. So I believe this is evidence that vaccines are working as intended. Thanks to Phil Kerpen on Twitter for the chart.
The virus may have run out of the frailest victims, while the strong survive. And a vaccine can’t hurt them at this point, and may help a lot.