When weighing the risk/benefit ratio of vaccinated with a killed, adjuvanted veterinary vaccine, the potential adverse reactions associated with the vaccine adjuvants should be considered.  While rabies immunization is required by law, some states accept rabies titers in lieu of vaccination -- for dog owners with that choice, the information below may persuade you that the higher cost of a rabies titer is preferable.
Leptospira, Lyme, and Rabies are killed, adjuvanted vaccines, which means that, unlike modified live virus vaccines (canine MLV's are distemper, hepatitis, and parvo), they cannot cause disease.  Adjuvants are components (such as aluminum hydroxide, aluminum phosphate) used to enhance the immunological response in killed vaccines.
 "The World Health Organization (WHO) in 1999 classified veterinary vaccine adjuvants as Class III/IV carcinogens with Class IV being the highest risk,"  (IARC Monographs on the Evaluation of Carcinogenic Risks to Humans:  Volume 74, World Health Organization, International Agency for Research on Cancer, Feb. 23-Mar. 2, 1999, p. 24, 305, 310.)
According to the 2003 American Animal Hospital Association's Canine Vaccine Guidelines http://www.leerburg.com/special_report.htm (page 16) "...killed vaccines are much more likely to cause hypersensitivity reactions (e.g., immune-mediated disease)."  Further, the AAHA task force reports on Page 18 that,  "Bacterial vaccines, especially killed whole organism products …..are much more likely to cause adverse reactions than subunit or live bacterial vaccines or MLV vaccines, especially if given topically.  Several killed bacterial products are used as immunomodulators/adjuvants.  Thus, their presence in a combination vaccine product may enhance or suppress the immune response or may cause an undesired response (e.g., IgE hypersensitivity or a class of antibody that is not protective)."
"Rabies is also the vaccine most likely to lead to an adverse event.  You should NEVER give Rabies at the same time as the other vaccines." according to an article in the October-December 2007, Vol. 26, #3 Journal of American Holistic Veterinary Medical Association, entitled: Summary of a Presentation by Dr. Ron Schultz,   written by Patricia Monahan Jordan, DVM .
Duration of Immunity to Canine Vaccines: What We Know and Don't Know, Dr. Ronald Schultz http://www.cedarbayvet.com/duration_of_immunity.htm
 What Everyone Needs to Know about Canine Vaccines, Dr. Ronald Schultz http://www.puliclub.org/CHF/AKC2007Conf/What%20Everyone%20Needs%20to%20Know%20About%20Canine%20Vaccines.htm 
World Small Animal Veterinary Association 2007 Vaccine Guidelines http://www.wsava.org/SAC.htm Scroll down to Vaccine Guidelines 2007 (PDF)
The 2003 American Animal Hospital Association's Canine Vaccine Guidelines are accessible online at http://www.leerburg.com/special_report.htm
The 2006 American Animal Hospital Association's Canine Vaccine Guidelines are downloadable in PDF format at http://www.aahanet.org/PublicDocumen...s06Revised.pdf .
Veterinarian, Dr. Robert Rogers,has an excellent presentation on veterinary vaccines at http://www.newvaccinationprotocols.com/