Lyme disease or Lyme borreliosis is a tick-borne zoonosis caused by bacteria of the genus Borrelia. This type of infection has been documented in dogs across several continents. In North America, the predominant canine cause is Borrelia burgdorferi (Bb).
In recent years, several commercially available vaccines have been developed for the prevention of canine Lyme disease. However, their use remains hotly debated. In this article, we discuss Lyme vaccines for dogs, their efficacy and safety, and the pros and cons of their use.
Canine Lyme disease: clinical signs and epidemiology
Dogs infected with Bb can suffer pyrexia, lymphadenopathy, anorexia, lethargy, and occasionally arthritis and glomerulonephropathy (“Lyme nephritis”), which can be fatal. Lyme nephritis is believed to be caused by circulating anti-Bb immune complexes but remains observationally correlated with infection rather than causatively proven. However, the majority (95%) of infected dogs show no clinical signs.
Bb seropositivity is around 5% in the US domestic dog population, although this reaches up to 100% in endemic hotspots. Exposure has been documented in all US states but is particularly prevalent in the North East, Upper Midwest and Mid-Atlantic states, with increasing cases on the West Coast. In Canada, nearly all known cases have occurred in regions bordering the US, especially in the Eastern provinces.
Lyme disease is transmitted by the hard-shelled Ixodes ticks. In the US and Canada, black-legged deer ticks (Ixodes scapularis) are responsible for most canine transmissions in the east, and Ixodes pacificus for those towards the west. Most cases occur in spring and summer owing to the seasonality of tick questing and increased dog walking, though ticks (and dog owners!) can be active in mild winters too.
Lyme disease vaccines for dogs
Tick prevention products are the mainstay of Lyme prophylaxis. Tick-to-dog Bb transmission takes around 36-48 hours from the time of attachment, and many ectoparasiticidal drugs can kill ticks within 24 hours. However, adjunctive vaccination may also be considered. Lyme vaccines are non-core, and there is a good consensus that they are not indicated outside of endemic areas.
Canine Lyme vaccines induce humoral immune responses to the Borrelia outer surface proteins (Osps). OspA provides adherence to the tick mid-gut. Upon feeding, the bacteria switch to production of OspC which allows migration to the parasite’s salivary glands – essential for transmission to a canine host. Vaccines contain either recombinant OspA and/or OspC proteins, or inactivated whole bacterial cells (bacterin).
In the US, there are five commercially available Lyme vaccines for dogs. Merial Animal Health Ltd and Zoetis Inc offer recombinant Osp protein subunit vaccines: Recombitek® Lyme and Vanguard® crLyme respectively.
Elanco Animal Health Inc, Merck Animal Health and Zoetis Inc offer bacterin vaccines with their Duramune® Lyme, Nobivac® Lyme and LymeVax® vaccines respectively. All Lyme vaccines except Recombitek® Lyme contain an adjuvant.
The licensed protocols call for two initial doses 2-4 weeks apart in dogs not younger than 8-9 weeks of age (manufacturer-depending), with single annual boosters recommended. However, the World Small Animal Veterinary Association (WSAVA) Vaccination Guidelines Group recommends vaccinating dogs no younger than 12 weeks of age against Lyme disease.
How effective are canine Lyme disease vaccines?
All Lyme vaccine manufacturers provide compelling data for the efficacy of their products in preventing infection. However, an independent study has shown waning of OspA-specific antibodies to levels seen in unvaccinated dogs by 10 months post-vaccination. This study included a selection of both subunit and bacterin vaccines. An off-license reduction in booster interval to six months has been suggested, though this is unassessed for safety.
A 2019 meta-analysis compiling observational and challenge studies concluded that dogs vaccinated against Lyme disease were less likely to develop some clinical signs (lameness, anorexia and fever) following Bb exposure. However, clinical signs were assessed in a binary absence/presence form, with no attention to severity or duration, and some studies included in the analysis failed to screen for subclinical infection before vaccination.
Zoetis Inc’s Vanguard® crLyme, a chimeric recombinant vaccine and the most recent to the US market, induces immune responses against OspA and seven variants of OspC shown to be present in Lyme seropositive dogs in the US. This may produce a broader anti-Bb immune response, and therefore in theory, increased subsequent protection.
What are the possible side effects and adverse reactions?
In a study by one manufacturer looking at an adjuvant-containing Osp subunit Lyme vaccine in over 600 dogs (receiving around 1200 doses), the most common immediate reaction noted was vocalisation upon injection, and the most common delayed adverse reaction was oedema at the site of administration.
Bacterin vaccines may pose a greater risk of adverse events than protein subunit vaccines. One study looking at vaccine-associated adverse events within three days of administration of a range of commonly used canine vaccines found the greatest number of events in a bacterin-based Lyme vaccine (0.44% of dogs vaccinated).
One theoretical serious adverse event is the possibility of inducing antigen-antibody immune complexes, which are believed to be the cause of polyarthritis and glomerulopathy in natural infection. However, in one study looking at use of a Lyme vaccine in nearly 2000 dogs in a Bb endemic area (many with prior Bb exposure), vaccination was considered safe. Anti-Bb antibodies in people have shown autoreactivity to self-antigens through molecular mimicry, which may also be possible in dogs, though never proven.
Weighing up the pros and cons of Lyme disease vaccines for dogs
The use of Lyme vaccines in at-risk dogs in endemic regions remains a contentious topic: in a 2018 consensus statement by the American College of Veterinary Internal Medicine (ACVIM) an equivocal panel of six experts voted three for and three against Lyme vaccination.
Proponents of Lyme vaccines assert that a track record for safety has satisfied the requirements of the US Food and Drug Administration (FDA) to enable their continued sale. It is also argued that owner compliance to uninterrupted tick prevention is rarely perfect, and annual vaccine coverage may help supplement this.
From a vaccine efficacy standpoint, the use of Lyme vaccines (of all varieties collectively) to reduce the likelihood of some clinical signs is supported by a recent meta-analysis. Lyme disease prevention is also more cost-effective than treatment (which can entail a long course of doxycycline plus other supportive care). Those endorsing vaccines often recommend their use in seropositive nonclinical animals, as previous natural infection does not produce protective immunity.
Opponents of Lyme vaccines assert that consistent tick preventive medications are robust, safe and reliable Lyme prophylaxis tools alone. It is also argued that mass vaccination isn’t warranted, since the vast majority of Bb infections in dogs cause no clinical disease at all.
Lyme vaccines carry the theoretical risk of immune-mediated adverse events, particularly polyarthritis or Lyme nephritis. The duration of immunity conferred from some vaccines has also been shown to fall significantly short of the 12-month booster period.
In conclusion, when evaluating the pros and cons of Lyme vaccines, it should be remembered that available vaccines are diverse and not created equally (e.g. recombinant protein vs bacterin) and therefore the appropriate scientific literature should be consulted selectively.
Lyme vaccines for dogs are not recommended outside of endemic regions. For animals residing in or travelling to known Lyme hotspots, vaccination remains at the clinical judgment of the veterinary practitioner on a case-by-case basis. Regardless of vaccination status, prophylactic ectoparasiticidal medications form the backbone of Lyme disease prevention.
Sources and additional reading
Lyme disease seroprevalence maps in dogs for the US and Canada. Companion Animal Parasite Council 2019 [Online]. Accessed April 2019. Available at: https://capcvet.org/maps/#2019/all/lyme-disease/dog/
WSAVA guidelines for the vaccination of dogs and cats. WSAVA, 2016 [Online]. Accessed April 2019. Available at:
Topfer KH, Straubinger RK. Characterization of the humoral immune response in dogs after vaccination against the Lyme borreliosis agent. A study with five commercial vaccines using two different vaccination schedules. Vaccine 2007. 25: 314-326.
Vogt NA, Sargeant JM, MacKinnon MC et al. Efficacy of Borrelia burgdorferi vaccine in dogs in North America: a systematic review and meta-analysis. Journal of Veterinary Internal Medicine 2019. 33: 23-36.
Moore GE, Guptill LF, Ward MP et al. Adverse events diagnosed within three days of vaccine administration in dogs. Journal of the American Veterinary Medical Association 2005. 227: 1102-1108.
Littman MP, Gerber B, Goldstein RE et al. ACVIM consensus update on Lyme borreliosis in dogs and cats. Journal of Veterinary Internal Medicine 2018. 32: 887-903.
Levy SA, Lissman BA, Ficke CM. Performance of a Borrelia burgdorferi bacterin in borreliosis-endemic areas. Journal of the American Veterinary Medical Association 1993. 202: 1834-1838.