One of my favorite podcasts to listen to while working outside is the
Chicken Thistle Farm Coop-Cast. For the past five or so years they have been raising pigs partly as a hobby business. With a large property and a max of two sows, they thought they would be able to raise their pigs on pasture without medications. The no medications thing was quickly abandoned, and just this year they threw in the towel and introduced a vaccination program for their pigs.
Another great pasture pig resource is Walter Jeffries of Sugar mountain farm. He uses heritage breeds on pasture with rotational grazing and even hangs out on the permies board from time to time, despite all that it looks as though he still vaccinates albeit not as heavily as the industrial farms:
Vaccines – I do believe in vaccination as preventative medicine. We vaccinate ourselves, our dogs and our kids. When I buy chicks I get them vaccinated for Merks Disease. I have not found it necessary to vaccinate the pigs as heavily as the literature suggests. Part of this may simply be that we are fairly isolated as well as the animals being outdoors in a low stress environment. For the sows I use FarrowSure Gold B or similar. If there were a disease outbreak in our area, I would vaccinate them as needed.
http://sugarmtnfarm.com/2007/02/01/piglet-interventions/