They will likely give you the same excuse as they do with measles: There are immune-deficient or allergic individuals who cannot get vaccines and if the rest of us don't get them we put those people at risk.

They will probably also use the excuse that those who do not get vaccines will continue to spread the COVID and it will mutate to the point where those who are vaccinated are no longer protected because the strains will be so different.

Take your pick.