I personally would rethink giving him lepto. The vaccination's effectiveness doesn't outweigh the risks IMO.
Vaccination against Leptospira interrogans is only available for the serovars called canicola, grippotyphosa, pomona and icterohaemorragiae. (Some vaccines cover all four serovars while others cover only two out of four.) As a result of long standing use of this vaccine, it is hard to assess how important it is to vaccinate against leptospirosis. Most recent outbreaks involve serovars for which vaccination does not exist.
CanineLeptospirosis