If new to sheep keeping remeber that if you buy from high health flocks and don't keep cats you probably won't need to vaccinate.
and none of your neighbours have or get kittens between now and lambing...
Yes, I had this discussion with my vet, who's a farmer's son from Cumbria and some relation to your BH, Sally, I seen to recall. I said we had old cats and didn't seem to have either. My ewes are all home bred.
He said his Dad definitely had no bother with these things either but once he vaccinated, his lambing % went way up
It's not expensive, it's a once in a lifetime vaccination - seems daft not to. Abortions would give me the heeby jeebies. I was freaking about Schmallenberg