No, it's not common for vaccines. That's a myth. Only the flu vaccine. It depends on the complexity of the mechanism of entering human cells. If the complexity

No, it's not common for vaccines. That's a myth. Only the flu vaccine. It depends on the complexity of the mechanism of entering human cells. If the complexity is simple, mutations are not likely to screw up that mechanism, and vaccines are quite short lived, like the seasonal flu. When the complexity is high, like measles, mutations have a much higher chance of screwing something up, so evolution is retarded and vaccines are effective for a lifetime. This issue is being so pigheaded as to think that 16 billion vaccines can be created, deployed, and put in arms in a short enough time span to defeat a brand new, somewhat fast evolving virus before it selects to get around the vaccine. It was never going to work.