This problem started in 2020, and started with Biden, Harris, Cuomo, etc questioning the safety of vaccines for political reasons. Then the disinformation about the disease and the vaccines followed by fascist policies that weren't followed by the very people pushing them created public mistrust. Trump was and has been the biggest advocate of vaccines, very consistently.
Scientifically and medically there was no reason to try to force CoVid vaccinations onto healthy children, the damage to public trust is done and will be difficult to reverse.
Guess what, we also imported a lot of unvaccinated people over the last 5 years. Do you think that may have a causal effect?
Link: https://pmc.ncbi.nlm.nih.gov/articles/PMC9746503/#:~:text=ABSTRACT,rates%20among%20diverse%20RIM%20populations.