The SARS-CoV-2 strain in Africa rendering vaccine useless is only a speculation based on evidence that the new strain escaped human antibodies in lab-cultured cells. But vaccines also induce T-cell immunity in addition to antibodies, so vaccines are most likely still effective. More info here if you'd to read further :))

https://shinjieyong.medium.com/the-most-worrying-coronavirus-e484k-mutant-has-arrived-35361ec55923