Backinwellies - I can't speak for MF, but we footvaxed our flock the winter before last, because we had a real problem with our sheep developing cracked hooves, which meant they then easily became infected with just about anything going.
To get control of the situation, we reluctantly footvaxed all of them (two jabs a few weeks apart). The jab was easy enough, but yes, there were a few pussy lumps which passed in time. I would agree with MF that this is best done outside flystrike season.
Since then, the incidence of scald in the lambs has decreased markedly (none at all last year, and only a couple of minor cases this year). We saw one incidence of footrot in a vaccinated ewe a couple of months ago, but it cleared up with alamycin very quickly. She is on her final warning, since I'm worried she could be a reservoir of infection which might then go on to affect others.
As mentioned elsewhere, we put out zinc rockies licks, which I believe have improved the strength of hooves. So this, coupled with a single course of footvax has given us the control we needed over the situation. We now seldom have to do anything with feet, whereas previously we were footbathing with goldenhoof+ every couple of weeks. If incidences of footrot started to recur in future, I would give them all a booster. However, this hasn't been necessary to date.
HTH!