From Middle English, from Old English efen, efn, emn â(â even, equal, like, level, just, impartial, true â), from Proto-Germanic *ebnaz â(â flat, level, even; equal, straight â), from Proto-Indo-European *(hâ)emno- â(â equal, straight; flat, level, even â).
1 Puppies can receive the injectable vaccine starting at 6 to 8 weeks of age, followed by a booster between 10 and 12 weeks of age. 2  For adult dogs or puppies older than 16 weeks, the intranasal vaccine can be given once, and the injectable vaccine should be given twice, two to four weeks apart. Kittens can be vaccinated intranasally as early as 8 weeks of age. 2  Puppies can receive the injectable vaccine starting at 6 to 8 weeks of age, followed by a booster between 10 and 12 weeks of age.
For pups, the initial vaccine is administered at 12 weeks old and repeated two to four weeks later. For older puppies (over four months old) or adults receiving the leptospirosis vaccine for the first time, two doses two to four weeks apart are recommended. Annual revaccination is recommended for dogs at sustained risk of exposure to the leptospirosis disease-causing organism. Dogs at exceptionally high risk should be vaccinated every six to nine months throughout the period of their continued high risk of exposure.