Background

The Strategic Advisory Group of Experts (SAGE) on Immunization was established in 1999 to provide policy and strategy advice on vaccines and immunization to the Director-General of the World Health Organization (WHO). SAGE is the principal advisory group to WHO for vaccines and immunization. All vaccine and immunization-related topics of public health relevance for which WHO requires strategic and policy advice need to be reviewed by SAGE.

This SAGE Working Group on Yellow Fever Vaccines (from now on referred to as SAGE WG) is established by the WHO SAGE Secretariat as a resource intended to support WHO in the preparation of SAGE deliberations by reviewing and providing evidence-based information and options for policy or strategy recommendations to be decided by SAGE. 

Terms of reference

The SAGE WG will be expected to formulate critical questions, as outlined below, for which an in-depth review of evidence is needed to address its workplan. With the support of the Secretariat, this Working Group will perform or coordinate, a systematic assessment of the evidence in accordance with the SAGE process for evidence–review and development of recommendations.

In its capacity as an advisory body to WHO, the SAGE WG shall have the following functions:

1. Support WHO in the development of evidence-based policy options and strategic recommendations on the use of fractional yellow fever vaccine doses
   

   Areas of focus will include:

   The global burden of disease caused by yellow fever virus infection, with a particular focus on outbreak dynamics.

   The impact of yellow fever vaccination in routine immunization programmes versus outbreak response (i.e., endemic use vs. reactive use).

   Safety, efficacy, immunological kinetics, and duration of protection of fractional-dose yellow fever vaccines, particularly in key subpopulations such as children, pregnant women, and older adults.

   Cost-effectiveness and programmatic considerations of the use of fractional versus full doses in the context of preventive and reactive campaigns.
   

2. Support WHO in the development of evidence-based policy options and strategic recommendations on one versus two lifetime doses.

Areas of focus will include:

Safety, efficacy, duration of protection, and co-administration of currently licensed yellow fever vaccines.

Waning of vaccine-induced immunity and breakthrough infections following a single dose, including age-dependent differences in immune response.

Comparative evaluation of the public health impact and cost-effectiveness of one versus two lifetime doses of yellow fever vaccine.

Composition

SAGE Members

• Glenda Gray (Chair), Wits university, South Africa
• Rebecca Grais, Pasteur Network, France

  Experts

• Anna Roukens, University Medical Center Leiden, the Netherlands
• Aitana Juan, Epicentre Paris, France
• Christopher Mayer. Independent expert, Australia
• Mathias Niedrig, German Accreditation Society, Germany
• Chinwe Iwu-Jaja, Independent expert, South Africa
• William Perea, Independent expert, Colombia
• George Warimbe, KEMRI Wellcome Trust Research Program, Kenya
• Joachim Hombach, Independent expert, Switzerland
• Antonio Camacho, Oswaldo Cruz Foundation, Brazil
• Erin Staples, Independent expert, USA
• Cheick Loucoubar, Institute Pasteur Senegal, Senegal
• Rakesh Aggarwal, Indian Council of Medical research, India
  

WHO Secretariat

• Annelies Wilder-Smith
• Laurence Cibrelus Yamamoto
• Judith van Holten
  

Declarations of Interest

All members completed a declaration of interests form. One SAGE member and five working group members reported relevant interests. Aitana Juan and George Warimbe were asked to recuse themselves from the recommendation-making on yellow fever fractional dosing. Luiz Anthonio Camacho was asked to recuse himself from the recommendation-making on yellow fever booster doses. It was assessed that the remaining working group members could participate fully in the deliberations of the Working Group. The reported relevant interests are summarized below:

Juan, Aitana

• Served as the principal investigator for the yellow fever vaccines fractional dosing trial (YEFE) until 2023. This interest was perceived as personal, specific and financially significant*
• Served as the co-investigator for the yellow fever vaccines fractional dosing trial (NIFTY) until 2024. This interest was perceived as personal, specific and financially significant*
• Serves as the co-investigator for a cholera second vaccine dose trail. This interest was perceived as non-personal, non-specific, and financially insignificant*.
  
  

George, Warimbe

• Serves as a member on the CEPI Scientific Advisory Committee. This interest was perceived as non-personal, non-specific, and financially insignificant*.
• Serves as a member on the GAVI working group on Dengue vaccines. This interest was perceived as non-personal, non-specific, and financially insignificant*.

• Served as the principal investigator for the yellow fever vaccines fractional dosing trial (NIFTY) until 2023. This interest was perceived as personal, specific and financially significant*
• Serves as the principal investigator of Phase 2 trial of ChAdOx1 RVF vaccine against Rift Valley Fever. This interest was perceived as non-personal, non-specific, and financially insignificant*.
• Served as the co- investigator for two Phase I trials of ChAdOx1 RVF vaccine against Rift Valley Fever until 2022. This interest was perceived as non-personal, non-specific, and financially insignificant*. 
  
  

Camacho, Luiz Antonio

• Serves as co- investigator of a cohort study on the duration of immunity of the yellow fever vaccine. This interest was perceived as personal, specific and financially significant*
  
  

  Roukens, Anna

• Serves as the principal investigator of a yellow fever prophylaxis trial. This interest was perceived as non-personal, specific, and financially insignificant*.
• Serves as the principal investigator of a pneumococcal vaccine trial. This interest was perceived as non-personal, non-specific, and financially insignificant*.
• Serves as the clinical supervisor of a BCG trial. This interest was perceived as non-personal, non-specific, and financially insignificant*.
• Served as the principal investigator of a COVID-19 trial until 2025. This interest was perceived as non-personal, non-specific, and financially insignificant*.
  
  

  Staples, Erin

• Serves as technical expert for yellow fever vaccine trials. This interest was perceived as non-personal, specific, and financially insignificant*.
  

Grais, Rebecca

• Serves as a Scientific Advisory Committee member of the Coalition for Epidemic Preparedness Innovations (CEPI). This interest was perceived as nonpersonal, non-specific and financially insignificant*.
• Served as a member until December 2025 at Institut Pasteur Dakar, Manufacturing in Africa for Disease Immunization and Building Autonomy (MADIBA) Project Steering Committee. This interest was perceived as nonpersonal, non-specific and financially insignificant*.
• Served until 2023 as a Data and Safety Monitoring Board (DSMB) member on Serum Institute of India for yellow fever vaccine. This interest was perceived as non-personal, non-specific and financially insignificant*.
• Served until December 2022 as sponsor of fractional dose of Pneumococcal Conjugate Vaccine (PCV), phase IV trial, funded by European & Developing Countries Clinical Trials Partnership (EDCTP). This interest was perceived as non-personal, non-specific and financially significant*.
• Serves as a member of the advisory board of MMGH Consulting. This interest was perceived as non-personal, non-specific and financially insignificant*.
• Served until 2023 as a DSMB member on Scandinavian Bio Pharma/EDCTP. This interest was perceived as non-personal, non-specific and financially insignificant*.
• Served as sponsor of fractional dose yellow fever, phase IV until 2022, funded by Wellcome trust, and the Médecins Sans Frontières (MSF) foundation. This interest was perceived as non-personal, specific and financially insignificant*
• Served until November 2022 as site investigator for effectiveness of Ebola vaccine, Phase II/III, funded by the Coalition for Epidemic Preparedness Innovations (CEPI). This interest was perceived as non-personal, non-specific and financially insignificant*.
• Served in 2023 on the International Vaccine Institute (IVI) Expert Panel on Hepatitis E vaccine in pregnant women. This interest was perceived as nonpersonal, non-specific and financially insignificant*.
  

* According to WHO's Guidelines for Declaration of Interests (WHO expert), an interest is considered "personal" if it generates financial or non-financial gain to the expert, such as consulting income or a patent. "Specificity" states whether the declared interest is a subject matter of the meeting or work to be undertaken. An interest has "financial significance" if the honoraria, consultancy fee or other received funding, including those received by expert's organization, from any single vaccine manufacturer or other vaccine-related company exceeds 5,000 USD in a calendar year. Likewise, a shareholding in any one vaccine manufacturer or other vaccine-related company in excess of 1,000 USD would also constitute a “significant shareholding”. As per the WHO assessment of conflicts of interests, “Institution” relates only to the expert’s research/or work unit as a subdivision of the department. Funding going to the SAGE Working Group member’s research unit needs to be declared