"Experts say" we have 9-12 months until the "first generation" vaccines are rendered totally ineffective by mutated strains:
https://www.cnbc.com/2021/03/30/mutations-could-make-current-covid-vaccines-ineffective-soon-survey.html
That's a big part of why we are waiting. We are at very low risk right now, and science will learn more about how the vaccine actually performs over the next year, leading to a better set of vaccines and more information about boosters, variants, etc. That's when we will jump in.