I don’t know how much of a tweak can be made without necessitating that a vaccine must go through the whole validation process again beginning with phase one clinical trials. The flu vaccine is altered on a yearly basis but that is only altering the already verified constituents of it. If a change is made to the actual antigenic part of a vaccine that would have to be shown to work and not signficantly increase side effects and/or complications.
“Is it not a bit late to be developing covid vaccines in/for Europe?”
Competition is healthy. The more vaccines available the cheaper they may become and I don’t think they have only Europe in mind. The EMA is the regulatory agency involved for Europe but I assume they are applying to other regulatory agencies around the globe.