Experts worry a South African variant of #Covid19 could be resistant to the new Covid vaccines, highlighting the principal concern of studies from 2018 over a vaccine\u2019s ability to trigger pathogens to evolve. While some experts believe this is another reason natural herd immunity is superior to temporary vaccine protection, self-proclaimed \u201cvaccine expert\u201d and tech billionaire, Bill Gates, says the solution is yet another vaccine dose.