Why is There Still no Human Vaccine Against Lyme Borreliosis?

Lyme disease, transmitted by ticks, is a complex illness that can be difficult to diagnose but easy to treat in most early cases, yet difficult in its latest stage. Every year, infections with Borrelia burgdorferi sensu lato spirochetes cause thousands of new cases of illness around the world, including people with a normal immunological reaction. Prevention in the form of vaccines is difficult due to e.g. very high variability of Borrelia antigen proteins, which precludes the construction of an effective vaccine. After the withdrawal of the OspA vaccine (LYMErix) in the USA, despite promising results, no vaccine protecting humans against all pathogenic species from the B. burgdorferi s.l. group is available. Recent data indicate that an effective vaccine may require a combination of several antigens or multiple epitopes based on vector-borne proteins and several outer membrane proteins of Borrelia. With the discontinuance of Lyme vaccines, personal protective behavior and the avoidance of exposure in high-risk areas remain necessary resources of prevention.