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BORRELIA BURGDORFERI, SEROTYPE 5, OUTER SURFACE PROTEIN A FUSED VIA A LINKER TO BORRELIA BURGDORFERI, SEROTYPE 6, OUTER SURFACE PROTEIN A, referred to here as Borrelia burgdorferi OspA vaccine or VLA15, is an investigational vaccine being studied for active immunization against Lyme disease.
Borrelia burgdorferi OspA vaccine (VLA15) is a protein-based vaccine that is still investigational, meaning it has not yet received marketing authorisation. It is a 6-valent vaccine, which means it is designed to target six different serotypes of Borrelia burgdorferi sensu lato, the group of bacteria that cause Lyme disease.[1] The vaccine contains outer surface protein A (OspA) from different Borrelia serotypes, fused together via a linker to create a single vaccine that aims to protect against multiple strains.
Lyme borreliosis is caused by multiple species of the spirochete bacteria Borrelia burgdorferi sensu lato. These bacteria are transmitted by ticks to vertebrate hosts, including humans.[3] The infection typically begins with a rash called erythema migrans at the tick-bite site, and if left untreated can progress to more severe conditions affecting the joints, heart, and nervous system.[2]
The vaccine is based on outer surface protein A (OspA), a protein found on the surface of Borrelia burgdorferi bacteria. Research has shown that OspA plays a role in host cell adherence and infection mechanisms: when Borrelia burgdorferi was treated with antibodies against OspA, the bacteria showed a significant decrease in their ability to associate with human cells.[2] This suggests that OspA helps the bacteria attach to and invade host cells, and that blocking this protein could interfere with infection.
VLA15 works by presenting OspA proteins from six different Borrelia serotypes to the immune system. The goal is to train the immune system to recognise and respond to these proteins, so that if a vaccinated person is later bitten by an infected tick, the immune system can block the bacteria from establishing an infection. The vaccine is designed to induce antibodies against OspA, which may prevent the bacteria from attaching to host cells and colonising tissues.
Studies have also shown that OspA expression is upregulated during the bacteria's interaction with host cells, further supporting its role in the early stages of infection.[2] Strain-to-strain variation in host-specific infectivity has been documented in Lyme borreliae, and surface protein polymorphisms may contribute to this variation.[3]
VLA15 is given as a 0.5 ml injection by intramuscular use, meaning it is injected directly into a muscle.[1] In the Phase 3 trial, the vaccine was compared with a placebo consisting of sodium chloride solution 0.9%, also given as a 0.5 ml intramuscular injection.[1] The trial involved a primary series of vaccinations followed by a booster dose.[1]
One completed Phase 3 trial (NCT05477524) has evaluated VLA15 in 9,400 participants for active immunization against Lyme disease.[1] The trial was placebo-controlled, meaning some participants received the vaccine and others received a placebo injection of saline solution.[1]
The trial measured three main types of outcomes. First, it assessed efficacy by determining whether VLA15 prevented clinically and laboratory confirmed Lyme disease caused by Borrelia burgdorferi sensu lato during the Lyme disease season after completion of the primary vaccination series and booster dose.[1] Second, it described the safety profile by recording local reactions at the injection site (pain, redness, swelling), systemic events (fever, headache, fatigue, muscle pain, joint pain), adverse events, and serious adverse events.[1] Third, it measured immunogenicity by testing anti-OspA antibody titers to show that immune responses to the six serotypes were equivalent across three independent manufacturing lots, and that responses in children aged 5–17 years were noninferior to those in adults aged 18–44 years after the booster dose.[1]
The sources provided do not report specific side effect results from the completed trial. The Phase 3 trial protocol included monitoring for local reactions at the injection site (pain, redness, and swelling) and systemic events (fever, headache, fatigue, muscle pain, and joint pain), as well as adverse events and serious adverse events, but the actual results are not described in the provided data.[1]
VLA15 is a 6-valent, protein-based vaccine designed to protect against Lyme disease. It contains outer surface protein A (OspA) from six different serotypes of Borrelia burgdorferi sensu lato, fused together via a linker. The vaccine is investigational, meaning it has not yet been authorised for use outside clinical trials.[1]
The Phase 3 trial enrolled 9,400 participants, making it a large study. Participants received either the VLA15 vaccine or a placebo (saline solution) by intramuscular injection. The trial is now completed.[1]
The trial measured three things: whether the vaccine prevented confirmed Lyme disease after the primary series and booster dose, the safety profile including local and systemic reactions, and immunogenicity, specifically whether antibody responses to all six serotypes were consistent across three manufacturing lots and whether responses in children aged 5–17 were noninferior to adults aged 18–44.[1]
The trial included both children aged 5–17 years and adults aged 18–44 years, as the immunogenicity analysis compared these two age groups after the booster dose. The trial enrolled a total of 9,400 participants.[1]
The trial is registered as NCT05477524 and can be found on ClinicalTrials.gov at https://clinicaltrials.gov/study/NCT05477524. The record contains the full protocol details, including the primary outcome measures and study design.[1]
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