Correlation of protection against varicella in a randomized Phase III varicella-containing vaccine efficacy trial in healthy infants

Background: Varicella vaccination confers high and long-lasting protection against chickenpox and induces robust immune responses, but an absolute correlate of protection (CoP) against varicella has not been established. This study models the relationship between varicella humoral response and protection against varicella. Methods: This was a post-hoc analysis of data from a Phase IIIb, multicenter, randomized trial (NCT00226499) conducted in ten varicella-endemic European countries. Healthy children aged 12–22 months were randomized 3:3:1 to receive one dose of measles-mumps-rubella and one dose of varicella vaccine (one-dose group) or two doses of measles-mumps-rubella-varicella vaccine (two-dose group) or two doses of measles-mumps-rubella vaccine (control group) six weeks apart. The study remained observer-blind until completion, except in countries with obligatory additional immunizations. The objective was to correlate varicella-specific antibody concentrations with protection against varicella and probability of varicella breakthrough, using Cox proportional hazards and Dunning and accelerated failure time statistical models. The analysis was guided by the Prentice framework to explore a CoP against varicella. Results: The trial included 5803 participants, 5289 in the efficacy (2266: one-dose group, 2279: two-dose group and 744: control group) and 5235 (2248, 2245 and 742 in the same groups) in the immunogenicity cohort. The trial ended in 2016 with a median follow-up time of 9.8 years. Six weeks after vaccination with one- or two-dose varicella-containing vaccine, more than 93.0% of vaccinees were seropositive for varicella-specific antibodies. Estimated vaccine efficacy correlated positively with antibody concentrations. The fourth Prentice CoP criterion was not met, due to predicted positive vaccine efficacy in seronegative participants. Further modelling showed decreased probability of moderate to severe varicella breakthrough with increasing varicella-specific antibody concentrations (ten-year probability <0.1 for antibody concentrations ≥2-fold above the seropositivity cut-off). Conclusions: Varicella-specific antibody concentrations are a good predictor of protection, given their inverse correlation with varicella occurrence. Clinical trial: NCT00226499

Generalized instantons in N = 4 super Yang-Mills theory and spinorial geometry

Using spinorial geometry techniques, we classify the supersymmetric solutions of euclidean ${\cal N}=4$ super Yang-Mills theory. These backgrounds represent generalizations of instantons with nontrivial scalar fields turned on, and satisfy some constraints that bear a similarity with the Hitchin equations, and contain the Donaldson equations as a special subcase. It turns out that these constraints can be obtained by dimensional reduction of the octonionic instanton equations, and may be rephrased in terms of a selfduality-like condition for a complex connection. We also show that the supersymmetry conditions imply the equations of motion only partially.Comment: 29 pages, 3 tables. v2: references added. v3: conclusion extended, version published in JHE

Vanishing Preons in the Fifth Dimension

We examine supersymmetric solutions of N=2, D=5 gauged supergravity coupled to an arbitrary number of abelian vector multiplets using the spinorial geometry method. By making use of methods developed in hep-th/0606049 to analyse preons in type IIB supergravity, we show that there are no solutions preserving exactly 3/4 of the supersymmetry.Comment: 19 pages, latex. Reference added, and further modification to the introductio

(1,0) superconformal theories in six dimensions and Killing spinor equations

We solve the Killing spinor equations of 6-dimensional (1,0) superconformal theories in all cases. In particular, we derive the conditions on the fields imposed by the Killing spinor equations and demonstrate that these depend on the isotropy group of the Killing spinors. We focus on the models proposed by Samtleben et al in \cite{ssw} and find that there are solutions preserving 1,2, 4 and 8 supersymmetries. We also explore the solutions which preserve 4 supersymmetries and find that many models admit string and 3-brane solitons as expected from the M-brane intersection rules. The string solitons are smooth regulated by the moduli of instanton configurations.Comment: 26 page

Maximally Minimal Preons in Four Dimensions

Killing spinors of N=2, D=4 supergravity are examined using the spinorial geometry method, in which spinors are written as differential forms. By making use of methods developed in hep-th/0606049 to analyze preons in type IIB supergravity, we show that there are no simply connected solutions preserving exactly 3/4 of the supersymmetry.Comment: 18 pages. References added, comments added discussing the possibility of discrete quotients of AdS(4) preserving 3/4 supersymmetry

All null supersymmetric backgrounds of N=2, D=4 gauged supergravity coupled to abelian vector multiplets

The lightlike supersymmetric solutions of N=2, D=4 gauged supergravity coupled to an arbitrary number of abelian vector multiplets are classified using spinorial geometry techniques. The solutions fall into two classes, depending on whether the Killing spinor is constant or not. In both cases, we give explicit examples of supersymmetric backgrounds. Among these BPS solutions, which preserve one quarter of the supersymmetry, there are gravitational waves propagating on domain walls or on bubbles of nothing that asymptote to AdS_4. Furthermore, we obtain the additional constraints obeyed by half-supersymmetric vacua. These are divided into four categories, that include bubbles of nothing which are asymptotically AdS_4, pp-waves on domain walls, AdS_3 x R, and spacetimes conformal to AdS_3 times an interval.Comment: 55 pages, uses JHEP3.cls. v2: Minor errors corrected, small changes in introductio

New half supersymmetric solutions of the heterotic string

We describe all supersymmetric solutions of the heterotic string which preserve 8 supersymmetries and show that are distinguished by the holonomy, ${\rm hol}(\hat\nabla)$, of the connection, $\hat\nabla$, with skew-symmetric torsion. The ${\rm hol}(\hat\nabla) \subseteq SU(2)$ solutions are principal bundles over a 4-dimensional hyper-K\"ahler manifold equipped with a anti-self-dual connection and fibre group $G$ which has Lie algebra, {\mathfrak Lie} (G)=\bR^{5,1}, \mathfrak{sl}(2,\bR)\oplus \mathfrak{su}(2) or $\mathfrak{cw}_6$. Some of the solutions have the interpretation as 5-branes wrapped on $G$ with transverse space any hyper-K\"ahler 4-dimensional manifold. We construct new solutions for {\mathfrak Lie} (G)=\mathfrak{sl}(2,\bR)\oplus \mathfrak{su}(2) and show that are characterized by 3 integers and have continuous moduli. There is also a smooth family in this class with one asymptotic region and the dilaton is bounded everywhere on the spacetime. We also demonstrate that the worldvolume theory of the backgrounds with holonomy SU(2) can be understood in terms of gauged WZW models for which the gauge fields are composite. The {\rm hol}(\hat\nabla) \subseteq\bR^8 solutions are superpositions of fundamental strings and pp-waves in flat space, which may also include a null rotation. The ${\rm hol}(\hat\nabla)=\{1\}$ heterotic string backgrounds which preserve 8 supersymmetries are Lorentzian group manifolds.Comment: 31 pages, minor corrections, analysis improved and more references adde

The spinorial geometry of supersymmetric backgrounds

We propose a new method to solve the Killing spinor equations of eleven-dimensional supergravity based on a description of spinors in terms of forms and on the Spin(1,10) gauge symmetry of the supercovariant derivative. We give the canonical form of Killing spinors for N=2 backgrounds provided that one of the spinors represents the orbit of Spin(1,10) with stability subgroup SU(5). We directly solve the Killing spinor equations of N=1 and some N=2, N=3 and N=4 backgrounds. In the N=2 case, we investigate backgrounds with SU(5) and SU(4) invariant Killing spinors and compute the associated spacetime forms. We find that N=2 backgrounds with SU(5) invariant Killing spinors admit a timelike Killing vector and that the space transverse to the orbits of this vector field is a Hermitian manifold with an SU(5)-structure. Furthermore, N=2 backgrounds with SU(4) invariant Killing spinors admit two Killing vectors, one timelike and one spacelike. The space transverse to the orbits of the former is an almost Hermitian manifold with an SU(4)-structure and the latter leaves the almost complex structure invariant. We explore the canonical form of Killing spinors for backgrounds with extended, N>2, supersymmetry. We investigate a class of N=3 and N=4 backgrounds with SU(4) invariant spinors. We find that in both cases the space transverse to a timelike vector field is a Hermitian manifold equipped with an SU(4)-structure and admits two holomorphic Killing vector fields. We also present an application to M-theory Calabi-Yau compactifications with fluxes to one-dimension.Comment: Latex, 54 pages, v2: clarifications made and references added. v3: minor changes. v4: minor change