Like Dot, we've been using it again the last few years, as orf cases had increased over the preceeding few years.
It works, but you do need to do it right and you do need to scratch all the lambs which will come into contact with the lambs that have been scratched and the places they have been. It's a live virus, so vaccinated lambs shed live virus which will infect unvaccinated sheep who come across it.
We do a double scratch to make sure it enters the lambs' systems - first scratch with the dose of vaccine; we do it in the 'lisk' but under the armpit works too, then, while the blue fluid is still visible, the second scratch, without pumping another dose onto the progs, but scratching across the first scratch, which makes absolutely sure that the vaccine enters broken skin.