Why do you mention mutation? Are you worried that mutation will evade vaccines? This hasn’t happened yet: the important new strains all appeared before there was much vaccination. They spread because they were generally more infectious, not because they infected people immune to the old variant. In particular, the trial of the beta-specific vaccine found that it took twice as many antibodies of of someone vaccinated with the original to defeat beta as antibodies of someone vaccinated with the beta vaccine. Twice isn’t a lot. The standard for flu vaccines for replacing vaccines with those targeting a new strain is a factor of eight.
Why do you mention mutation? Are you worried that mutation will evade vaccines? This hasn’t happened yet: the important new strains all appeared before there was much vaccination. They spread because they were generally more infectious, not because they infected people immune to the old variant. In particular, the trial of the beta-specific vaccine found that it took twice as many antibodies of of someone vaccinated with the original to defeat beta as antibodies of someone vaccinated with the beta vaccine. Twice isn’t a lot. The standard for flu vaccines for replacing vaccines with those targeting a new strain is a factor of eight.