Unfortunately, there is no real nexus between the seriousness of a disease and the effectiveness or safety of a vaccine for that disease. In my opinion, the Lyme vaccine does not actually provide enough benefit to outweigh its substantial risks, despite the seriousness of canine Lyme Disease.
The Lyme vaccine can cause an untreatable form of Lyme disease and, like all bacterial diseases, provides short term immunity. It is not recommended at any of the vet schools in the United States. The human Lyme vaccine was withdrawn from the market. For all the reasons, I think that it's best avoided. But I have one more, very compelling reason.
There are other tick borne diseases that are much more serious than Lyme, for which we have no vaccines. So even if a very safe and effective Lyme vaccine were developed for dogs, having your dog vaccinated for Lyme isn't going to lessen the need for tick prevention. So it's hard to make the risk vs. benefit analysis for Lyme vaccination come out on the benefit side, no matter how you work the math.
http://www.caberfeidh.com/Lyme.htm