Thus, we have so far not been able to perform vaccine efficacy studies in mice with VLA15 against (ST3). VLA15-induced antibodies provide protection against five Inauhzin OspA serotypes upon passive immunization In addition to active immunization, we have also assessed protection provided after passive immunization with pooled immune sera from mice immunized three times with two week intervals, with 5.0 g VLA15 formulated with 0.15% aluminium hydroxide. against challenge with four different clinically relevant species (and species and OspA serotypes (ST) present in Europe and the US, namely (ST1), (ST2), (ST3, ST5 and ST6) and (ST4) . The VLA15 vaccine is based on the notion that the C-terminal part of OspA is sufficient to induce protective immunity . Therefore, by using the C-terminal part of six OspA serotypes (ST1 to ST6) stabilized with disulfide bonds, and linking two monomers together in each of the three fusion proteins, we have generated a new LB vaccine for global use . Furthermore, introducing a lipid moiety IMPA2 antibody at the N-terminus of each fusion protein and formulating the vaccine with aluminium hydroxide strongly increased the immunogenicity in mice . The vaccine induced a Inauhzin protective immune response against challenge with grown (ST1) or (ST5) as well as with ticks infected with Inauhzin (ST2) . We could also demonstrate the induction of a functional immune response with surface binding for all OspA serotypes and growth inhibition assays for five of the six OspA serotypes included in the vaccine . In order to improve the OspA ST3 specific immunogenicity as well as the yield of the fusion protein representing OspA ST3 and ST4, a modified protein was designed . In the new fusion protein, referred to as Lip-D4Bva3B, approximately 1/3 of the N-terminal part of the OspA ST3-monomer has been exchanged with the corresponding sequence of OspA from species. The studies have used either grown (ST1) [9,10], (ST5)  or (ST6) . Alternatively using laboratory reared ticks infected with either (ST1)  or (ST2) [6,13]. We have now been able to assess the efficacy of VLA15 following challenge with species expressing five different OspA serotypes; (ST1), (ST2), (ST4) or (ST5 and ST6). Protection against the first three mentioned species was assessed in challenge models where the Inauhzin natural vector, ticks, were used for challenge of VLA15 immunized mice. Tick challenge models for (ST3, ST5 and ST6) have thus far not been described. Growth inhibition assays were described for the OspA serotypes 1, 2, 4, 5 and 6 by us [6,8] and others . However, a functional assay with ST3 has still been missing, likely because the spirochetes were sensitive to the guinea pig match alone, and this source of match was generally used in the assay as founded by Sadziene and coworkers . By further development of our growth inhibition assay, we were able to study the bactericidal effect of anti-VLA15 immune sera with regards to (ST3). OspA is definitely expressed in tradition and on the spirochete surface when in the tick gut. It is down regulated once the tick begins to feed and is replaced by OspC on the surface. Anti-OspA antibodies take action in the tick gut to block transmission. Therefore, safety is dependent on a sufficient level of circulating anti-OspA specific antibodies. In order to avoid frequent booster immunizations, a strong and long-lasting immune response is definitely desired [15,16]. In 2002, at the time when LYMErix was withdrawn from the market, it was not known how long a protective immune response would last. Consequently, it was not identified at what interval booster immunization would be required [5,17]. LYMErix was given with a routine of 0, 1 and 12 months. One month after the third immunization, subjects experienced a GMT of Inauhzin 6,000 enzyme immunoassay devices (EIA U)/mL and 90% of those experienced a titer 1,400 which ensures safety over one tick time of year. Nearly all subjects that got infected experienced an anti-OspA antibody titer 400 EIA U/mL at the time of LB onset [18,19]. Consequently, we assessed the antibody titers induced by VLA15 in mice for one year and identified the effect of a booster immunization given five months after the main immunization. In this article we demonstrate remarkably broad protection in several novel mouse models following VLA15 immunization and challenge with infected ticks or cultivated spirochetes unsurpassed by any preceding LB vaccine [20C22]. In addition, data describing the induction.