I use Scour-Gard, given to the cow about 8 weeks before calving, works very nicely.
about 18 years ago we lost about 3 calves and had about 8 more sick out of 20, it was a misery! Since we've vaccinated, we've had maybe a case every 5 years, and most of those were weak calves that didn't get much colostrum.
It's the only vaccine I use, I have a pretty isolated herd that doesn't get to rub noses with any strange cows.. I would vaccinate with 7 way if I had shared fencelines or close neighbors... As Aaron said, 1 loss would pay for years and years of vaccine.