Send to

Choose Destination
Vaccine. 2019 Jul 18;37(31):4376-4381. doi: 10.1016/j.vaccine.2019.06.019. Epub 2019 Jun 24.

An online decision tree for vaccine efficacy trial design during infectious disease epidemics: The InterVax-Tool.

Author information

Department of Epidemiology and Biostatistics, University of Georgia, Athens, GA, USA; Center for Ecology of Infectious Diseases, University of Georgia, Athens, GA, USA. Electronic address:
Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK. Electronic address:
World Health Organization, Geneva, Switzerland.
Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK.
Department of Biostatistics, University of Florida, Gainesville, FL, USA.
Department of Geography, University of Kentucky, Lexington, KY, USA.
Kenya Medical Research Institute, Centre for Global Health Research, Kisumu, Kenya.
Centre de recherche du CHU de Québec, Québec, Canada; Département de médecine sociale et préventive, Université Laval, Québec, Canada; Department of Infectious Disease Epidemiology, Imperial College, London, UK.
Centers for Disease Control and Prevention, Atlanta, Georgia, USA.



Licensed vaccines are urgently needed for emerging infectious diseases, but the nature of these epidemics causes challenges for the design of phase III trials to evaluate vaccine efficacy. Designing and executing rigorous, fast, and ethical, vaccine efficacy trials is difficult, and the decisions and limitations in the design of these trials encompass epidemiological, logistical, regulatory, statistical, and ethical dimensions.


Trial design decisions are complex and interrelated, but current guidance documents do not lend themselves to efficient decision-making. We created InterVax-Tool (, an online, interactive decision-support tool, to help diverse stakeholders navigate the decisions in the design of phase III vaccine trials. InterVax-Tool offers high-level visual and interactive assistance through a set of four decision trees, guiding users through selection of the: (1) Primary Endpoint, (2) Target Population, (3) Randomization Scheme, and, (4) Comparator. We provide guidance on how key considerations - grouped as Epidemiological, Vaccine-related, Infrastructural, or Sociocultural - inform each decision in the trial design process.


InterVax-Tool facilitates structured, transparent, and collaborative discussion of trial design, while recording the decision-making process. Users can save and share their decisions, which is useful both for comparing proposed trial designs, and for justifying particular design choices. Here, we describe the goals and features of InterVax-Tool as well as its application to the design of a Zika vaccine efficacy trial.


Decision support system; Emerging infectious diseases; Epidemics; Outbreaks; Phase III trial; Public Health Emergency; Scientific communication; Vaccine trial design; Vaccines

Supplemental Content

Full text links

Icon for Elsevier Science Icon for PubMed Central
Loading ...
Support Center