How Lyme Disease Vaccines Work in Dogs

Some Lyme disease vaccines work inside the tick—before the bacteria ever enter the dog.

Lyme disease vaccines in dogs are designed to block transmission of Borrelia burgdorferi before infection can take hold.

Lyme disease is the most common tick-borne disease affecting both humans and dogs. According to the Companion Animal Parasite Council (CAPC), 319,000 canines tested positive for Lyme disease in 2018—up from 160,000 in 2012. The true number is likely higher, as data is collected from only about 30% of tests performed.

Understanding how these vaccines work helps explain both their strengths—and their limitations.

The Role of OspA and OspC Proteins

The Lyme spirochete expresses different surface proteins depending on where it is in its life cycle.

In ticks, the bacteria produce Outer Surface Protein A (OspA). After transmission to mammals, the organism shifts to producing OspC.

This transition is central to how vaccines are designed.

OspA-Based Vaccines

Recombitek Lyme, produced by Boehringer Ingelheim, contains only OspA proteins.

“Anti-OspA antibodies inhibit transmission from ticks to mammals by targeting spirochetes in the tick midgut,” explains Izac.

This means the vaccine works before the bacteria enter the dog, blocking infection at the level of the tick.

The human vaccine LYMErix, introduced in 1998 and withdrawn in 2001, was also based on OspA.

OspA + OspC Combination Vaccines

Some newer vaccines, such as VANGUARD crLyme, include both OspA and OspC components.

These vaccines aim to provide two layers of protection:

Targeting bacteria in the tick (OspA)
Targeting bacteria in the mammal after transmission (OspC)

“A vaccine that induces antibody that can kill spirochetes in both ticks and mammals has the potential to use two synergistic mechanisms of protection,” the authors explain.

There is currently no human vaccine using this combined approach.