have worked exceedingly well, resulting in a major reduction in cases, etc, up until Spring time of this year...then, the Delta variant rapidly became the dominant strain with much higher transmissibility and at a time when folks were feeling the need to "Open Up" and mingle...then came a surge in cases/hospitalizations/deaths...that's life in the virus vs. vaccine game...so, booster shots are the logical response.
...also, most vaccines require "booster shots" to maintain immunity...even the Seasonal Flu requires a newly formulated shot every year...it's not at all unusual.
Just be glad you have vaccines, and the technology to rather rapidly 're-formulate' them, should the need arise due to another variant...I hope we don't need it, but it's under discussion as we speak.
As for the other maladies, they are not "Communicable" diseases...so no need for mandates...you can relax now...at least on that concern.
Note: Conor's NYT link earlier shows the COVID cases dynamic over time...you can see what happened in graphic detail.