The flu mutates every single year, but we don't have a global flu-based culling every single winter season because we've developed an immune response to viruses that are *like* it. Some people die every year, but catching the flu or the common cold is no longer a world-shattering event for *most* people. A vaccine is like a punching bag - it's not just like punching someone, but it lets you learn some technique without breaking your knuckles in the process. Depending on the mutation the efficacy may be reduced, but we're not talking about one strain completely replacing the other, we're dealing with both simultaneously. It's not a this or that, it's both, at the same time. This should motivate you to take it *more*, not less, as your odds of contracting the virus have increased, not decreased.