If I understand it right, mRNA isn't so much exactly hard, as bespoke. It's a new technology and not many places are fitted out to make it. It can eventually be

If I understand it right, mRNA isn't so much exactly hard, as bespoke. It's a new technology and not many places are fitted out to make it. It can eventually be expected to become much cheaper. And mRNA can keep up with flu. It can also target things in a more deliberate way, if I understand it. So a protein could be selected that is common to many variants and hard for the virus to do without.