I only vaccinate for worms, a month before farrowing so there is a degree of transfer across to the piglets and the piglets again when they are weaned, the piglets also get an iron injection as I farrow inside.
There is a big push towards reducing the amount of microbials used on animals as there may be a knock on effect reducing immunity within the food chain, the days of treating every possible thing has gone and you should only treat where necessary, such as worming, anything else should be treated on an as and when basis.
There is a tendency to think you will get every disease under the sun, but this is not normally the case, and when good hygiene and husbandry is employed your animals will have an enjoyable life.