To answer the WHY question. In the U.S. many are suspicious of the government's motivation based upon disease risk versus vaccine risk. Accurate statistics by age groups are not available and there is a marked distrust about the vaccines' effectiveness. The current public conviction is: that the SARS-Cov-2 virus was most likely manufactured in the Wuhan Lab as a surreptitious joint effort that was inappropriately managed. Consequently, governments don't really know what can happen. That being said. The vaccines in the U.S. have been demonstrated to be effective at both preventing and mitigating covid-19 and its current variants. Those with questions about the vaccines should consult their doctors and do their research.