Leptospirosis is now classified as a core vaccine for dogs. The American Animal Hospital Association (AAHA) updated its 2022 canine vaccination guidelines to include the leptospirosis vaccine alongside distemper, parvovirus, adenovirus, and rabies as vaccines recommended for all dogs regardless of lifestyle.
This is a relatively recent change, and it’s why you’ll still find conflicting information online. For years, lepto was considered non-core, meaning it was only recommended for dogs with specific risk factors. Here’s what shifted and what it means for your dog.
Why the Classification Changed
Leptospirosis is a bacterial infection that can cause acute kidney injury, liver disease, lung hemorrhage, and death in dogs. It’s also zoonotic, meaning infected dogs can pass it to people. There is no human vaccine available in the United States, so vaccinating dogs serves as a frontline defense for both species. A 2023 CDC report on a human case linked to a canine outbreak stated directly that increased vaccination coverage protects both dogs and the people exposed to them.
The disease has historically been associated with rural dogs that swim in ponds or encounter wildlife, but cases now appear in suburban and urban areas too. Flooding, standing water near homes, contact with wildlife urine, and even walking through puddles are all documented transmission routes. As the geographic spread of leptospirosis has widened, the old model of vaccinating only “high-risk” dogs left too many unprotected.
What Major Veterinary Organizations Recommend
AAHA’s 2022 guidelines are clear: the killed 4-serovar leptospirosis vaccine is core, recommended for all dogs unless there’s a specific medical reason not to vaccinate. This puts it in the same category as rabies and distemper.
The World Small Animal Veterinary Association (WSAVA) took a slightly different approach in its 2024 guidelines. Previous WSAVA guidelines categorized lepto as non-core, but the updated version now states that in countries or regions where canine leptospirosis is endemic and suitable vaccines are available, vaccination of all dogs is “highly recommended” and the vaccine “should be considered core.” For most of the United States, Canada, Europe, and many tropical regions, that threshold is met.
Your vet may still describe lepto as non-core if they’re working from older protocols or if you live in an area with very low incidence. But the direction of both major guideline bodies is toward universal vaccination.
What the Vaccine Covers
Current leptospirosis vaccines are 4-serovar products, meaning they protect against four of the most common bacterial serogroups that cause disease in dogs: Canicola, Icterohaemorrhagiae, Australis, and Grippotyphosa. These cover the majority of clinical infections, though other serogroups do circulate at lower levels.
Unlike some core vaccines that provide years of protection, leptospirosis immunity fades relatively quickly. Annual boosters are required to maintain coverage. If your dog’s last lepto vaccine was 18 or more months ago, most guidelines recommend restarting the initial two-dose series rather than giving a single booster, as a precaution.
Vaccination Schedule for Puppies and Adults
Puppies can receive their first dose as early as 8 weeks of age, with a second dose given 2 to 4 weeks later. Both doses are needed for initial protection. After that, a single booster is given every 12 months.
Adult dogs that have never been vaccinated for lepto follow the same two-dose starter series, spaced 2 to 4 weeks apart, followed by annual boosters.
Vaccine Safety and Side Effects
The lepto vaccine has a reputation for causing more reactions than other vaccines, but large-scale data paints a more reassuring picture. A study published in the Journal of the American Veterinary Medical Association tracked adverse event rates across thousands of dogs and found that the overall rate of owner-reported reactions was about 53 per 10,000 dogs that received a leptospirosis vaccine (alone or combined with other vaccines), compared to 26.3 per 10,000 for dogs in general after any vaccination visit.
The more important finding concerned allergic-type reactions specifically. Hypersensitivity reactions occurred at a rate of 8.5 per 10,000 dogs that received the lepto vaccine, compared to 6.2 per 10,000 dogs that did not. That difference was not statistically significant, meaning the lepto component did not measurably increase the risk of a true allergic reaction. Most reported side effects are mild: soreness at the injection site, low energy, or a slight fever for a day or two.
Small-breed dogs do tend to have higher reaction rates to vaccines in general, not just lepto. Some vets address this by giving the lepto vaccine at a separate visit from other shots, reducing the overall immune challenge at one time.
Risk Factors That Make Vaccination Especially Important
Even though lepto is now considered core for all dogs, certain situations carry higher risk. Dogs with any of the following exposures have a greater chance of encountering the bacteria:
- Water exposure: swimming in lakes, rivers, or stagnant water; walking through puddles or flooded areas; drinking from standing water sources
- Wildlife contact: areas frequented by raccoons, rats, or other small mammals whose urine contaminates soil and water
- Rural or semi-rural living: proximity to livestock, farms, or wooded areas
- Recent heavy rainfall or flooding: leptospirosis outbreaks spike after storms and floods
- Dog parks and shared outdoor spaces: any area where multiple animals urinate increases environmental contamination
Urban dogs are not exempt. Rats are a major carrier, and any city with a rodent population has leptospirosis circulating in the environment. Dogs that walk on sidewalks where rats have urinated, or that drink from puddles in parks, have real exposure risk.
What Leptospirosis Looks Like in Dogs
Infection ranges from mild and subclinical to life-threatening. Acute kidney injury is the most common presentation in recent years, sometimes accompanied by liver damage. Dogs may show vomiting, lethargy, loss of appetite, increased thirst and urination, muscle stiffness, or reluctance to move. Some develop a cough or difficulty breathing from pulmonary hemorrhage, though this is less common in dogs than in humans with the disease.
Early treatment with antibiotics significantly improves outcomes, but kidney or liver damage can be permanent. The disease progresses quickly, and dogs can go from seemingly fine to critically ill within days. Vaccination remains far simpler and safer than treatment.