There are hundreds of different leptospiral strains (serovars). Lepto vaccines traditionally only contain two serovars - canicola and icterohaemorrhagiae. However, studies show that most cases of lepto in dogs involve the serovars pomona and grippotyphosa, which made the lepto vaccine virtually ineffective. Vaccines that protect against pomona and grippotyphosa are now available. If you are going to have your dog or cat vaccinated against lepto - be sure that the vaccine protects against those two strains.