Heptavac P Plus is what you want, it will protect against a whole number of diseases that can affect both ewes and lambs. It's an insurance policy almost, as with most of the diseases it will protect against the first symptoms are death... pretty nasty. The pre lambing booster will give immunity to lambs through the ewe's milk for the first 6ish weeks of life. After that you need to get the lambs onto the system by 2 jabs 4-6wks apart. In order to get on the system the ewes will need 2 jabs of Heptavac 4-6 weeks apart, and then their annual booster at lambing. So if you get it done now, and then give them the pre lambing dose 4-6 wks before lambing begins, then in subsequent years you'll only need to do the lambing dose. The vaccine must be used within 8 hours of opening the bottle, so you'd need 2 bottles and the smallest bottle is 25 dose bottles unless you (or your vet) can find someone local who you could share with. The jabs go under the skin on the neck- a bit fiddly to do so I would suggest investing in the auto injector rather than using a needle and syringe- this will help reduce abscesses too as it sterilises the needle on each application. Definitely worth doing though, and the lambs too even if they are just going in the freezer.