>I remember that in March somebody posted here an entry saying that mutation of the virus will make vaccinations only useful in the short term. Were these concerns already addressed at this stage?

Regardless of whether the mutations are significant enough to affect vaccine efficacy, it won't likely be a problem. These new mRNA vaccines have a development/production time measured in weeks and months, not years. It changes vaccines from a hardware problem to a software problem. Once the underlying delivery technology is proven safe and effective, reacting to new strains will be as swift as patching a codebase. It's hard to overstate what a massive advance in vaccine tech is happening here.