Is the Leptospirosis vaccine dangerous?

25 February 2022 - 2 min read
Dog getting vaccinated

Dogs in the UK used to be vaccinated with a leptospirosis vaccine known as  L2, but in 2014 the L4 vaccination was introduced, and with it some controversy over safety.

The difference between these two jabs is that  L4 protects agains four strains of Leptospirosis and L2 only protected against two.

So why do some pet owners think the Leptospirosis vaccine is dangerous? Unfortunately social media reports of side effects circulated after the change to L4, which has made some owners question whether they should get the jab for their dog.

A cat waving whilst a dog hides its face

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A cat waving whilst a dog hides its face

“All preventative products can potentially cause an adverse reaction in our pets,” says Veterinary Surgeon Dr Sophie Bell. “But this is usually due to an underlying condition specific to that pet and their immune system. Thousands of dogs are vaccinated annually with no adverse reactions.”

The Veterinary Medicine Directorate quickly responded by pointing out that "the incidence of adverse animal reactions for all L2 vaccine products combined is 0.015%; for L4 vaccine products this figure is 0.069%."

So although some people have picked up on this increase you can see that the chance of a pet having a reaction is still tiny.

In the UK, the British Small Animal Veterinary Association (BSAVA) states the vaccine is a core vaccine, but that’s not the case in other parts of the world where it’s considered non-core. That means it’s only given if the animal in question is considered to be at particular risk from its environment. The kennel cough vaccine is an example of a non-core vaccine in the UK.

Why should my pet have the Leptospirosis vaccine?

The only alternative to regular boosters is titre testing. Titre testing is a technique used to look for antibodies against a certain virus or bacteria. It’s available for distemper, hepatitis, and parvovirus, but not leptospirosis antibodies.

That means the vaccine is the only way to reliably keep your dog safe from leptospirosis.

Leptospirosis bacteria is zoonotic, which means it can spread to humans from animals. And it can be deadly.

What can Leptospirosis cause?

  • Jaundice

  • High body temperature

  • Muscle aches

  • Vomiting and diarrhoea

  • Abdominal pain

  • Death

How can my dog get Leptospirosis?

Dogs can contract leptospirosis by drinking stagnant water from puddles, being bitten by an infected animal or through open wounds if they encounter urine-contaminated water.

Dogs that go on to show clinical signs sadly do not always survive. Although it is not a common condition, it is seen in the UK.


Digby Bodenham
UK engagement team lead

Digby is an experienced journalist in various fields but has specialised in insurance for more than six years. Before joining ManyPets in 2013 he was part of the editorial teams of various magazines, including Retail Week and Drapers. He has a degree in journalism and a cat called Potato.