We treat our whole herd every six months with Virbamec for mange/lice/worms etc. We vaccinate against Erysipelas and Porcine Parvo Virus, you can get a combined vaccine that does them both its called Porcilis Ery + Parvo, after the initial dose you then repeat after a fortnight and then we do ours every six months, personally I don't inject my pigs with it if they are heavy in pig, we start the program when they are gilts, and only inject gilts/sows after they have farrowed or dry. We do the boars as well as it can effect there fertility. Erysipelas is always present in pigs, it gets triggered off by certain things, stress, hot muggy weather, how they are kept, birds are a carrier of the disease, so try and keep feed etc bird free, its a nasty little disease which can kill pigs very easily, if you ever get it inject with Pen Strep and you will see the lesions dissapear more or less before your eyes, once a pig had had it they become very immune to it, Erysipelas and Parvo cause abortions, dead stillborn/mummified piglets, fertility problems in your boars and sows, low litter sizes. To be honest with you there is a whole host of vaccines you can inject your pigs with but to me the above are the most important to me. There is nothing more distressing for the sow and owner seeing her give birth to 10 or 12 dead piglets, when routine vaccinations can help prevent it..
Hope that helps...