RNA viruses, like Sars, frequently have small changes in their genome. As of September 2020, over 1000 changes were found in Sars-Cov-2 which can be different in different parts of the world. These changes were found by testing. By now there are over 2000 changes.
The RNA is the coding for parts of the physical properties of the virus. The vaccine’s target is the spike protein on the surface of the virus and causes our immune system to create antibodies to this. So far, the spike protein on the outside of the virus has not been physically changed enough by these changes in the virus genes but it could. The scientific community is actively testing all over the world and communicating.
The sooner we stop the spread of COVID-19, the less likely it will continue to change to become more virulent or change so much the vaccines will not work and we have to start over. Wear a good mask, socially distance, do not socialize with people inside who do not live with you, socially distance and be outside with people you do not know, sanitize your hands after touching anything outside your home. Get vaccinated when it is offered to you. YOU CAN BE PART OF THE SOLUTION.