That's partly because other countries vaccinated children. Believe israel started at the end of july.
The problem mainly seems to be that the pfizer vaccine doesn't last that long (for actually catching the disease, you will still have more mild disease). Boosters for the elderly and at risk have been brought in and cases are falling again.
Now the big question is. If you have been vaccinated is it better to be exposed to the disease and have a mild case or have a booster. I believe israel had a study that getting the virus after vaccination give 13times the protection.
We'll see. I 1 off studies can be misleading.