From the “Angry Vet ” blog:

Spaying and Neutering

We need to bring to light the truths behind spaying and neutering your pets.  The big push to spay and neuter our pets, in particular before puberty, was brought about as a response to the explosion of stray animals without homes.  These strays ultimately have to be euthanized at shelters so it was a valiant effort to address a real problem.

– See more at: http://www.angryvet.com/spaying-and-neutering/#sthash.rNDUP5If.2h3mKq6p.dpuf

and if you go to the site to read the short article on spay /neuter there is also an easy to read brief post  on vaccines:

http://www.angryvet.com/vaccinations/

What he says about the Lepto shot is true it can be very hard on the dog and should not be given to a puppy under 4 months.  It is not a vaccine but a bacterin so the effectiveness is short lived.  Lepto around certain areas in Michigan is recommended every 6 months.   Lepto had virtually disappeared from our radar as a serious issue when out of no where two new deadly strains popped up and healthy dogs were dying.  It was being passed by the urine of raccoons, possums,  and other rodents. These two new strains were referred to as  P & G; Pomona and Grippotyphosa

For more info on the various strains of Lepto:

http://www.peteducation.com/article.cfm?c=2+2102&aid=454

Check with your vet and find out if there have been outbreaks of Lepto in your area and then decide to give the shot or not.