One hundred years ago, Albert Calmette (1863–1933) and Camille Guérin (1872–1961) had almost reached their goal (1). They had passaged Mycobacterium bovis 200 times at 14 d intervals on potato slices soaked with ox gall in their attempt to generate an attenuated vaccine against tuberculosis (TB). They had started their program in 1906 and had already obtained preliminary evidence for safety and protection of their candidate in 1913. Yet, they continued until they had completed the 230th passage before verifying its efficacy and safety in experimental animals including guinea pigs, rabbits and non-human primates (NHPs) as well as in the natural host, cattle. The data obtained were highly promising so Calmette and Guérin started the first vaccination of a human neonate born into a household with a TB patient. Risk of TB in a household-contact infant at those times was extremely high. Yet, the baby did not develop TB and after additional encouraging results, vaccinations of more than 20,000 neonates in households with at least one TB patient were performed between 1921 and 1924. The results of this trial revealed that of the vaccinees 5% had died and 1% of these of TB, whereas knowledge of the time held that a quarter of non-vaccinated newborns would die in the first years of life, many of them of TB (1). This is the start of Bacille Bilié Calmette-Guérin, later shortened to Bacille Calmette–Guérin (BCG), which remains the only licensed vaccine against TB until today. Although not perfect, this vaccine partially fulfills the goal set by Calmette and Guérin, since it protects against extra-pulmonary forms of disease in infants, including life threatening TB meningitis. Unfortunately, in most settings, BCG does not reliably prevent pulmonary TB, the most prevalent and the most contagious form in all age groups from the neonatal to the elderly population. The lack of an efficient vaccine against pulmonary TB is a major obstacle to control TB satisfactorily until today.

In 1993, the World Health Organization (WHO) declared TB a global emergency at a time when some 4–6 million new TB cases per year were notified. With the introduction of a new treatment regimen, called directly observed treatment, short-course (DOTS) program, WHO claimed to bring TB under control and predicted a decline from 6–8 million new cases in 1997 to 2–3 million new cases by 2017 by implementing highly intensive DOTS (2). Unfortunately, this hope failed miserably. The most recent notifications reveal a stunning 10.4 million new cases and 1.8 million deaths in 2015. Building on better drug regimens alone not only proved to be insufficient in controlling TB, it also led to increasing incidences of multi-drug-resistant forms of TB.

At this time, researchers interested in the mechanisms underlying immunopathology and immune protection of TB were concerned that the efficacy of DOTs might be overestimated and considered a better TB vaccine a necessity for efficient TB control. Thus, a proposal on TB vaccines was submitted to the European Commission (EC) funded framework program (FP) 5 and this was funded from 1998 to 2002. The subsequent FP 6 and FP 7 programs continued to support TB vaccine-related research until 2013. During this period, enormous progress was achieved, not only resulting in the development of a number of promising vaccine candidates but also providing deeper understanding of immune mechanisms underlying protection and pathology in TB as well as identifying new TB biomarkers (BMs). These FP5 to FP7 activities were succeeded by the Horizon 2020 program which further supported TB vaccine research and development. It is this continuous support over the past 20 years which has welded together researchers from all over Europe and other parts of the globe to harness cutting-edge knowledge in the immunology, microbiology, and high end technology platforms for the development of novel TB vaccine candidates. This sustained EC funding made it possible to establish a unique European consortium responsible for most of the global innovation in TB research.

This EC-funded activity proved extremely successful. Over 50% of the global pipeline in TB vaccine candidates currently evaluated in clinical trials originate from EC funded projects (3). The EC has played a key leadership role in accelerating TB vaccine research and development and ensured a well-coordinated and efficient TB vaccine research consortium.

At the same time, the pipeline needs to be fed constantly with new innovative candidates since it is unlikely that one single vaccine could protect against all different forms of TB disease in all age groups and for all indications. Thus, the concept of diversification gained increasing importance. Different vaccine types (subunit vaccines vs. whole cell vaccines), different administration schedules (pre-exposure vs. post-exposure), different age groups (neonates vs. adults) and different purposes (prevention of infection vs. disease vs. recurrence of disease), and perhaps even therapeutic TB vaccines have all to be considered.

Already before the beginning of TBVAC2020, it was realized that an isolated vaccine development approach was inadequate and needed to be complemented by deeper knowledge of patho-mechanisms, immunology, and microbiology; by established as well as novel animal models; by identifying biosignatures of TB disease, risk of disease, vaccine efficacy, and safety (3–6). Finally, with increasing numbers of vaccines being ready for clinical testing, early clinical trials needed to be integrated. Although TBVAC2020 and its predecessors respect individual researchers’ autonomy, it was deemed of increasing importance to also provide a portfolio management process, including consensus gating criteria, to objectively and transparently guide further product and clinical development of TB vaccine candidates (7). This article describes the different activities of the Horizon 2020 funded TBVAC2020 project which is coordinated by TBVI summarizing recent achievements and future goals as part of the European effort to successfully combat TB. Figure 1 provides an overview of the close interactions between different WorkPackage (WP) activities and progression of promising vaccine candidates from discovery via preclinical testing to clinical trial. Although TBVI has coordinated much of the European research efforts on TB vaccine development to date, there are other ongoing activities, for example, through the Aeras Foundation¹ and the EMI-TB Consortium.²

A major objective of TBVAC2020 is the identification of novel vaccine candidates for subsequent preclinical and early clinical development. To this end, the objective of WP1 is to develop innovative approaches and platforms for TB vaccination in three areas: (i) the discovery of novel antigens and live vaccines; (ii) the exploration and implementation of novel immunization strategies and vaccination platforms; and (iii) the optimization of formulation and delivery of available subunit and live vaccine candidates.

In the absence of unambiguous markers that correlate with and, thus, predict vaccine-induced protective immunity against Mtb infection and TB disease (31, 32), experimental infection models remain an indispensable tool in the process of TB vaccine research and development. And while at present no animal-free systems exist that fully recapitulate the complexity of host defense cascades and pathogenesis (33), it is imperative to exploit animals at various (staggered) stages of this vaccine Research and Development (R&D) process and in particular to demonstrate vaccine efficacy (34).

Typically, several lower and also higher vertebrate animal species are utilized as models from as early as discovery up to building qualification dossiers and down selecting the best candidate vaccines toward resource-consuming, advanced stage clinical testing (Phase II and later) (35). These models are not only used to investigate the protective efficacy against an infectious challenge but also to assess vaccine tolerability (or, in specific cases, attenuation of live vaccines as a parameter of vaccine safety) and immunogenicity of new approaches, which build upon or extend beyond the current BCG vaccine.

Strictly speaking, no single animal model has been validated for the ultimate predictive assessment of TB vaccines toward the various target populations that can be identified globally. Models by definition imply a simplification of real-life complexity. Especially in the light of developing new preventive/prophylactic vaccine strategies, we, therefore, explore candidate vaccine performance in several different models to strengthen its proof-of-concept and to de-risk the development process for possible failures (35). In recognition of the undoubted limitations of any specific model, centralized and independent preclinical evaluation modalities are established in mouse, guinea pig, and NHP hosts, as described in WP3.1.

Mostly, preclinical studies assess the prophylactic profile of vaccine candidates in healthy animal hosts, which are experimentally challenged with Mtb and that are immunologically naive to mycobacterial antigens and typically free from any other disease or infectious pressure. In the clinic, pre-exposure, co-infection, and/or co-morbidity conditions can be expected to have an impact on susceptibility and also vaccine efficacy (36). The TBVAC2020 consortium, which at this point just passed mid-term of its 4-year work program, has set out in a specific WP to develop and refine models toward various clinically relevant conditions. Grossly, we have defined three areas as follows: (A) modeling vaccination conditions post-Mtb exposure, (B) modeling disease risk factors and clinically relevant conditions, and (C) refinement of existing models. With an eventual goal of implementing alternative models to provide proof-of-concept in support of preclinical vaccine development and candidate portfolio management, animal studies are explicitly useful also for investigating fundamental aspects of TB infection and immunity and may contribute to the identification and validation of BM candidates as one of the other key objectives of this consortium (covered in WP5).

The overall aim of WP3 is to support and facilitate the progression of vaccine candidates from discovery through to preclinical development. This is achieved in two sub-WPs. WP3.1 enables the selection of successful candidates through comparative head-to-head testing in standardized animal models. These studies provide crucial information for vaccine developers and also support activities in WP3.2 which aim to take the prioritized, most promising preclinical TB vaccine candidates and accelerate their advancement through the TB vaccine pipeline. WP3.2 provides expertise in all aspects of product development which enables relevant advice via tailor-made Product and Clinical Development Teams (P&CDTs) to be given to developers in order to advance their candidates in an efficient manner. Specific issues are identified and guidance/recommendations are given to developers. Close interaction between the sub-WPs is essential to ensure effective use of resources and this is facilitated by the Portfolio Management Committee (PMC) (WP6).

Demonstration of the safety, immunogenicity, and efficacy of vaccine candidates in animal models is required for preclinical development. This WP aims to provide evidence that the candidate is safe and elicits:

an immune response that can be justified as being anti-mycobacterial and is of appropriate magnitude in terms of strength and duration, compared to a benchmark such as BCG;

Systematic, independent, and objective comparison of TB vaccines in well-characterized animal models enables the identification of the vaccines that have the greatest potential to be immunogenic and to show efficacy in the clinic. WP3.1 provides capacity for animal testing, building upon the concept that was developed in previous FP5, FP6, and FP7 projects for head-to-head comparisons of candidates in standardized animal models. In addition, there is an aim to offer models that better represent the target product profiles of the vaccines being developed.

The objective of WP3.1 is to compare and prioritize vaccines from the candidate discovery work package of this project (WP1) which supports decision-making at the individual partner and WP level and provides objective evidence for decision-making in portfolio management using the stage-gating criteria (WP6). Wherever feasible, samples are retained for selected evaluation of potential correlates of protection (CoP; WP5). The partners providing the models all have experience and a track record in TB R&D and importantly are recognized providers of unbiased, high quality evaluation of vaccines in their respective models. A summary of each of the models provided is given below.

Up to June 2017, 51 tests (comprised of 21 different vaccine candidates/approaches) of safety, immunogenicity and/or efficacy have been completed (33 tests) or are on-going (18 tests) in the various models. Outcomes of completed studies are summarized below:

In the standard mouse or guinea pig challenge models, three candidates have shown protective efficacy and four were not efficacious.

These data (both positive and negative) have informed the portfolio management (WP6) and supported the vaccine discovery activities (WP1).

The main objective of this sub work package is to manage and facilitate the advance of the preclinical development pathway of new TB vaccine candidates. It supports the progression of the pipeline by advancing candidates prioritized through preclinical toward an early clinical stage of development using a portfolio management approach (as described in WP6). Tailor-made P&CDTs, including experts in regulatory, manufacturing, and clinical studies of vaccines, are established together with the selected vaccine developers. Currently, there are four vaccine candidates in preclinical development. For HBHA and BCGΔzmp1 candidates, joint P&CDTs with Aeras (as part of the joint global effort in TB vaccine development) have also been established to support these candidates in the context of the activities of this project. More information about the P&CDT can be found in the chapter describing WP6.

Early phase I and first-in-man clinical testing is an essential bridge between the demonstration of safety and efficacy in preclinical animal models and field testing in clinical trials in TB endemic countries. Such early clinical testing focuses on evaluating safety, usually in healthy adults, and immunogenicity, using a variety of standardized immunological assays. The overall concept underpinning WP4 is that standardized early clinical testing is essential, given the increasing numbers of diverse candidate TB vaccines being evaluated in preclinical animal models. There is currently a significant portfolio of diverse candidate vaccines in clinical and late preclinical development, which illustrates the progress made over the last 15 years (60). With the increasing number of diverse candidate vaccines currently in preclinical development, it is important to develop standardized methods and facilities for early clinical testing, in order that the most promising candidates can be selected for progression. There will never be sufficient resources to progress all the current candidates through to field testing in TB endemic countries. The use of standardized clinical trial protocols, standardized safety reporting, and standardized immunological evaluation according to published recommendations will allow comparison between different candidate vaccines (61, 62). This comparison will facilitate the rational selection of which candidates should be progressed to further clinical testing and efficacy testing in field trials. The aim of WP4 is to focus on early clinical TB vaccine development and to build on the successful standardized preclinical vaccine testing developed in EC supported FP6 TBVAC and FP7 NEWTBVAC projects. Over the last 10 years, the TBVAC/NEWTBVAC consortia have conducted many standardized head-to-head preclinical animal studies in mice, guinea pigs and NHPs. The data arising from these studies have facilitated vaccine selection (63, 64). This WP takes this successful approach a step further and applies it to early clinical testing.

Furthermore, there is an opportunity provided by this WP to embrace human experimental medicine studies, where early clinical trials can be used to demonstrate proof-of-concept. An example of this would be the evaluation of the safety and immunogenicity of a recombinant viral vector delivered by aerosol, compared with systemic administration (65).

Vaccine candidates are selected for inclusion in this WP by the PMC, in conjunction with the TBVI P&CDT. This advice is independent of the vaccine developer. TBVI and Aeras have agreed on a set of portfolio management criteria which include stage-gating criteria (7, 34), and these criteria are used to guide vaccine selection in this WP4. The data arising from the trials conducted as part of this WP4 will be reviewed by the PMC for subsequent decisions about progression to safety and immunogenicity trials in TB high burden countries. Ongoing interactions with The European & Developing Countries Clinical Trials Partnership (EDCTP) and clinical sites in Africa, including those that are part of the EDCTP Networks of Excellence, will ensure that, subject to full and independent peer review, promising candidates are progressed as efficiently and effectively as possible in an endemic setting. Support and advice by tailor-made P&CDT will be provided to each vaccine developer to accelerate the development of the respective vaccine candidates through phase I/first-in-man clinical trial stage.

Although we do not have an immunological correlate of protection with which to guide vaccine design and evaluation, there are several well-defined parameters of the host immune response which are known to be essential for protective immunity against Mtb. The immunological evaluation will be conducted using standardized operating procedures (SOP). Assays will include ex vivo IFNγ ELISpot assays, whole blood polychromatic flow cytometry with intracellular cytokine staining to measure other T cell cytokines, including IL-2, TNF-α, and IL17 from antigen-specific CD4⁺ and CD8⁺ T cells, and serological testing for antibody responses. The focus of this immunological evaluation is to use standardized assays to generate information about immune functions considered to be important in protective immunity. Work conducted within FP6 TBVAC, FP7 NEWTBVAC, and FP7 TRANSVAC has resulted in a harmonized SOP for an ex vivo ELISpot, which will be used here (66). In addition, a harmonized ICS flow protocol developed in these consortia will be used here as well (67). We will not use more exploratory assays in this WP, as they are less standardized, but PBMC and serum will be stored from all subjects at all time-points using harmonized SOP, so that further immunological evaluation can be performed as the field of BMs develops. In this regard, this WP will work closely with WP5 to monitor progress in the field of BM development (4, 5, 40, 41). Furthermore, ongoing work, for example, within the infrastructural FP7 EURIPRED project, to standardize the PBMC mycobacterial growth inhibition assay (MGIA), will be monitored and this assay will be conducted on cryopreserved material if the assay is deemed sufficiently fit for this purpose (68).

There are two broad categories of vaccines currently in development: “live” whole organism BCG replacement vaccines and subunit vaccines designed to boost BCG. Some live vaccines are also being evaluated as booster candidates (69, 70). It is anticipated that both types of candidate vaccines will be included and tested within this WP. Centre Hospitalier Universitaire Vaudois (CHUV), Leiden University Medical Center and University of Oxford clinical trial units will be collaborating in the planning and execution of the future candidate vaccine testing. Clinical and immunological SOPs have been agreed between the three partners. Following an open call to all partners, a first vaccine candidate has been selected and is planned to enter into phase I testing in CHUV in Q4 2017. It is expected that a second candidate will be tested in Q1 2018.

Next to TB vaccine development and evaluation, an important second TBVAC2020 objective is to identify TB BMs, in particular CoP. CoP are measurable BMs indicating that the host is immune, or protected against developing TB disease. Correlates of Risk (CoR) are BM indicating the host has an increased risk of developing active TB disease. Such TB BMs can be transcriptomic, cellular, or soluble analytes. The identification of CoP in particular will help to develop vaccines that target and strengthen protective immunity. Importantly, such correlates will facilitate the selection and prioritization of candidate TB vaccines for human efficacy testing, and will reduce the protracted time scale, size, and expenses of human efficacy trials by allowing the demonstration of vaccine immunogenicity and potential efficacy at an early stage. In addition, CoP will permit selection of antigens that induce protective immune responses, optimization of dose, vehicle, adjuvants, and immunization schedules of new candidate vaccines at an early stage and, thus, minimize the need for preclinical animal studies. WP5 has a strategically designed workflow, which combines TB BM discovery with parallel-specific assay development, followed by testing and validation in carefully characterized, complementary and unique human cohorts from genetically diverse populations. WP5 involves key partners from European, African, and East Asian laboratories.

This WP first aims to develop core assays for measuring CoP and CoR (#1 in Figure 2) and to evaluate these in carefully characterized, unique human cohorts from genetically diverse populations (#2 in Figure 2). Complementary to these efforts is the discovery of new TB BMs, using innovative approaches (#3 in Figure 2). A long-term goal is to move the best performing correlates forward toward validated immune correlate assays, ideally in the format of point-of-care tests for use in areas with high TB burden. Future activities will include active engagement of assay developers. Finally, the WP5 is building a database to capture the most important (transcriptomic) TB BMs (#4 in Figure 2), and there are close interactions between this WP and other efforts in this area.

The first key objective is the development, evaluation, and improvement of core assays measuring CoP in TB. To identify TB vaccine-induced CoP a protective vaccine is needed, but with the exception of BCG in settings where it does induce protection, this is not yet available. As BCG is able to induce partial protection, studies dissecting BCG-induced BMs are part of WP5. Moreover, a number of candidate correlates have recently emerged: BCG-vaccinated TB-protected South African infants had higher numbers of IFNγ-producing cells, and antibodies to Mtb antigen Ag85A also correlated with reduced risk of developing TB (40, 41). Other candidate CoR have been emerging (71), including myeloid/lymphoid (M/L) ratios (72), inflammation signaled by activated CD4⁺ T cells (40, 41), an IL13/AIRE ratio in HIV Mtb co-infected individuals (73), the lack of IFNγ responses to HBHA (74, 75), and a 16-gene based transcriptomic GC6/ACS CoR signature (76) found in large cohort studies in Africa. In other joint work by WP5 partners, diagnostic transcriptomic- or serum host protein signature-based algorithms were discovered that have powerful differential diagnostic value in diagnosing TB in both adults and children in Africa (77–79). Several research groups in WP5 are involved in efforts to further validate these correlates in larger, independent cohort studies.

In parallel to attempts identifying CoP, WP5 participants are developing unbiased, functional measures of human protective responses. One example of such an assay is the in vitro MGIA (68). In BCG-vaccinated infants in the UK, there was an increased ability to control the growth of BCG following BCG vaccination (43). Other “unbiased” assays include global immune-, gene expression-, and proteomic profiling-assays, which are being evaluated against outcome of infection or vaccination in clinical cohorts. We anticipate that the development and optimization of novel functional read-outs of anti-mycobacterial immunity will help identifying novel correlates, and may lead to deeper insights into potential mechanisms that control mycobacterial outgrowth. Collaborative efforts are ongoing with other EC projects, such as the FP7 EURIPRED Infrastructure project, as well as with EDCTP-funded work that focuses on TB BMs (PREDICT TB and SCREEN TB projects). Together, critical assays and assay variables are being identified to enable the development of improved, quantitative second generation assays. MGIA assays are also being studied for utility in analyzing cellular activity in human Purified Protein Derivative of Mtb suction blister models, in broncho-alveolar lavage (BAL) samples from aerosol BCG-infected volunteers and in the NHP model (80).

The second objective of WP5 is the evaluation of these core assays in samples from clinical cohorts. Such cohorts that have been collected include:

samples from BCG-vaccinated individuals (adults, children, neonates) from settings where BCG gives good protection against TB (northern Europe);

The unique cohorts and sample banks suitable for the measurement and evaluation of correlates are available for study in WP5 and are being further expanded, including cohorts with long-term longitudinal follow-up. Multiple cohorts have been included to represent geographical, ethnic, and epidemiological diversity, with sites from South Africa, Malawi, The Gambia, Uganda, South Korea, Western/Southern Europe (UK, Netherlands, Belgium, Italy) and Eastern Europe (Belarus). This will also make it possible to test whether TB BMs, including CoR and CoP, show variation by population due to specific epidemiological settings.

The third objective of the WP5 is the discovery of new TB candidate BM using innovative approaches. Given the lack of CoP, BM discovery is needed to fill the TB BMs pipeline with new candidates. It is likely that multi- rather than single parameter signatures, or complex functional assays will be needed to capture the complexity and dynamics of human protective immunity to Mtb. Discovery approaches are focusing on both host and pathogen response during the different phases of infection. These include global transcriptomics, proteomics, metabolomics, hematopoietic (myeloid) progenitor analyses, epigenetic, and cellular approaches. In other projects partners are developing intradermal as well as aerosol BCG controlled human infection models (CHIM). Such studies will allow for identifying and measuring immune correlates, and help with correlating in vivo with in vitro results, e.g., results from CHIM with corresponding MGIA studies. To date, significant progress has been made in transcriptomic marker identification in several cohorts, with further data analysis and validation ongoing.

Assays have also been selected to survey the wider global space in the immune response to Mtb rather than the traditional focus on T cells and cytokines, similar to approaches in HIV correlates research. Different compartments of the “immune space” being investigated include adaptive immunity (T cells, B cells, immune regulatory cells), innate immunity [innate lymphocyte-subsets, DC-subsets, macrophages (83), tolerogenic monocytes, myeloid-derived suppressor cells (84)], NK cell subsets, dysregulation of apoptosis or autophagic flux (85), the role of particular immunometabolomic and proteomic markers (86) (in blood or other body fluids) etc. Recent findings point to an important role for: antibodies and B cells in TB (40, 41, 87, 88); a role for HLA-E restricted Mtb specific CD8⁺ T cells (89, 90); and polycytotoxic LAM-specific T cells (91).

The longer-term strategy of WP5 is to select the most promising markers and assays for further development toward user friendly, preferably point of care, tests (92). Partners have expertise in downstream assay development such as lateral flow assays (86) and simplified transcriptomic assays (71). Recent novel work on mathematical modeling of vaccine immune responses has shown that models can predict dose–response relationships (93).

An important point is that TB BM assays may need to be adapted to specific types of TB vaccines (e.g., live vs. subunit) or depending on the antigen and delivery system selected. This may necessitate “tailor made” sets of BMs, for which TBVI is setting up a BM Development Team (BDT).

Finally, WP5 is building a TB transcriptomic biomarker database, to be a helpful resource for the TB BM community to provide a basis for “tailor made” TB vaccine biomarker selection, and to complement a TB diagnostic BM database as a valuable resource for future research (94).

WorkPackage 5 also links to other activities in TBVAC2020, including animal models (mice, NHPs) and human clinical vaccine trial related TB BM assays; and some of WP5 partners actively participate in these activities.

WorkPackage 5 aims to discover new TB BM (of protection and TB risk) using innovative approaches including omics studies; to develop and improve key functional assays; and, importantly, to initially validate and then cross-validate candidate TB BMs in human cohorts (95). The long-term goal is to test and provide data on the biological validity of the BMs discovered and the assays developed using cohorts in whom protection will be demonstrable and to evaluate them against clinical endpoints (including incident TB and Mtb infection). The unique combination of researchers, expertise, technologies and human cohorts for validation studies is key to the success of this ambitious task.

The TBVAC2020 consortium consists of 42 partner institutions from 15 countries, including 10 from Europe, 1 from USA, 1 from South Korea, 1 from Australia, 1 from the Gambia, and 1 from South Africa represented by the following members:

Australia: Warwick Britton (W.J. Britton), University of Sydney, Autralia; Jamie Triccas (J.A. Triccas), University of Sydney, Autralia; Claudio Counoupas (C. Counoupas), University of Sydney, Autralia. Belgium: Johan Grooten (J. Grooten), Ghent University, Belgium; Marie-Ange Demoitie (M.A. Demoitié), GSK Biologicals, Belgium; Marta Romano (M. Romano), Scientific Institute of Public Health (WIV-ISP), Belgium; Kris Huygen (K. Huygen), Scientific Institute of Public Health (WIV-ISP), Belgium; Hermann Giresse Tima (HG. Tima), Scientific Institute of Public Health (WIV-ISP), Belgium; Francoise Mascart (F. Mascart) , Université Libre de Bruxelles, Belgium. Denmark: Peter Andersen (P.L. Andersen), Statens Serum Institut (SSI); Claus Aagaard (C. Aagaard), Statens Serum Institut (SSI); Dennis Christensen (D. Christensen), Statens Serum Institut (SSI); Morten Ruhwald (M. Ruhwald), Statens Serum Institut (SSI); Thomas Lindenstrom (T. Lindenstrom), Statens Serum Institut (SSI). France: Olivier Neyrolles (O. Neyrolles), Centre National de la Recherche Scientifique (CNRS); Pierre Charneau (P. Charneau), Institut Pasteur Paris; Christophe Guilhot (C. Guilhot), Centre National de la Recherche Scientifique (CNRS); Antonio Peixoto (A. Peixoto), Centre National de la Recherche Scientifique (CNRS); Martine Gilleron (M. Gilleron), Centre National de la Recherche Scientifique (CNRS); Isabelle Vergne (I. Vergne), Centre National de la Recherche Scientifique (CNRS); Camille Locht (C. Locht), Institut Pasteur de Lille; Roland Brosch (R. Brosch), Institut Pasteur Paris; Genevieve Inchauspe (G. Inchauspé), Transgene; Stephane Leung Theung Long (S. Leung-Theung-Long), Transgene. Germany: Stefan Kaufmann (S.H.E. Kaufmann), Max Planck Institute for Infection Biology; January Weiner (J. Weiner), Max Planck Institute for Infection Biology; Jeroen Maertzdorf (J. Maertzdorf), Max Planck Institute for Infection Biology; Natalie Nieuwenhuizen (N. Nieuwenhuizen), Max Planck Institute for Infection Biology; Max Bastian (M. Bastian), Friedrich-Loeffler-Institut; Steffen Stenger (S. Stenger), University of Ulm; Stephanie Kallert (S. Kallert), University of Ulm. Ireland: Stephen Gordon (S.V. Gordon), University College Dublin. Italy: Nadia Caccamo (N. Caccomo), Azienda Ospedaliera Universitaria Policlinico “Paolo Giaccone” di Palermo; Delia Goletti (D. Goletti), IRCCS Lazzaro Spallanzani; Roberto Nisini (R. Nisini), Istituto Superiore Di Sanità (ISS). Republic of Korea: Sung Jae Shin (S.J. Shin), Yonsei University College of Medicine; Sang Nae Cho (Ray) (S.N. Cho), Yonsei University College of Medicine; Hyejon Lee (H. Lee), International Tuberculosis Research Center; Ino Choi (I. Choi), International Tuberculosis Research Center. South Africa: Alex Sigal (A. Sigal), Kwazulu-Natal Research Institute for Tuberculosis; Thomas Scriba (T.J. Scriba), South African Tuberculosis Vaccine Initiative; Gerhard Walzl (G. Walzl), Stellenbosch University; Andre Loxton (A.G. Loxton), Stellenbosch University; Robert Wilkinson (R.J. Wilkinson), University of Cape Town; Katalin Wilkinson (K.A. Wilkinsons), University of Cape Town. Spain: Pere-Joan Cardona (P.J. Cardona), Fundació Institut d’ Investigació en Ciències de la Salut Germans Trias i Pujol; Cris Vilaplana (C. Vilaplana), Fundació Institut d’ Investigació en Ciències de la Salut Germans Trias i Pujol; Carlos Martin (C. Martin), University of Zaragoza; Dessi Marinova (D.V. Marinova), University of Zaragoza; Nacho Aguilo (N. Aguilo), University of Zaragoza. Switzerland: François Spertini (F. Spertini), Centre Hospitalier Universitaire Vaudois; Ruedi Aebersold (R. Aebersold), ETH Zürich – Institute of Molecular Systems Biology; Etienne Caron (E. Caron), ETH Zürich – Institute of Molecular Systems Biology; Daniel Pinschewer (D. Pinschewer), University of Basel; Gennaro De Libero (G. De Libero), University of Basel; Claire Anne Siegrist (C.A. Siegrist), University of Geneva; Nicolas Collin (N. Collin), University of Lausanne; Christophe Barnier-Quer (C. Barnier-Quer), University of Lausanne; Peter Sander (P. Sander), University of Zürich. The Gambia: Jayne Sutherland (J.S. Sutherland), Medical Research Council. The Netherlands: Frank Verreck (F.A.W. Ferreck), Biomedical Primate Research Centre (BPRC); Tom Ottenhoff (T.H.M. Ottenhoff), Leiden University Medical Center (LUMC); Simone Joosten (S.A. Joosten), Leiden University Medical Center (LUMC); Krista van Meijgaarden, Leiden University Medical Center (LUMC); Mariateresa Coppola, Leiden University Medical Center (LUMC); Annemieke Geluk, Leiden University Medical Center (LUMC); Nick Drager (N. Drager), Tuberculosis Vaccine Initiative (TBVI); Danielle Roordink (D.M. Roordink), Tuberculosis Vaccine Initiative (TBVI); Jelle Thole (J. Thole), Tuberculosis Vaccine Initiative (TBVI). United Kingdom: Yvonne Perrie (Y. Perrie), University of Strathclyde; Marc Baird (M.S. Baird), Bangor University; Michael Levin (M. Levin), Imperial College, Faculty of Medicine, Department of Medicine & School of Public Health; Myrsini Kaforou (M. Kaforou), Imperial College, Faculty of Medicine, Department of Medicine & School of Public Health; Hazel Dockrell (H.M. Dockrell), London School of Hygiene and Tropical Medicine (LSHTM); Steven Smith (S.G. Smith), London School of Hygiene and Tropical Medicine (LSHTM); Helen Fletcher (H.A. Fletcher), London School of Hygiene and Tropical Medicine (LSHTM); Gregory Bancroft (G.J. Bancroft), London School of Hygiene and Tropical Medicine (LSHTM); Ann Rawkins (A. Williams), Public Health England; Simon Clark (S. Clark), Public Health England; Sally Sharpe (S. Sharpe), Public Health England; Mei Mei Ho (M.M. Ho), The Department of Health, UK, acting through PHE and MHRA; Helen McShane (H. McShane), University of Oxford; Iman Satti (I. Satti), University of Oxford; Elena Stylianou (E. Stylianou), University of Oxford; Rachel Tanner (R. Tanner), University of Oxford; Martin Vordermeier (H.M. Vordermeier), Animal and Plant Health Agency (APHA); Philip Hogarth (P.J. Hogarth), Animal and Plant Health Agency (APHA). United States of America: Danilo Casimiro (D. Casimiro), Aeras.

The mentioned investigators have all conducted and/or contributed to the R&D activities of TBVAC2020 project described in this manuscript.

All authors contributed to the writing and editing of the manuscript.

SK is co-inventor of BCG DureC::hly (VPM1002). BP is affiliated with RegExcel Consulting Ltd. All other authors have no other potential conflicts of interest to disclose.