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 (from now on referred to as SAGE WG) will be 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 requested to work on specific issues and address critical questions related to yellow fever vaccination. It will review the scientific evidence and relevant programmatic considerations to formulate draft recommendations on the use of yellow fever vaccines. The draft recommendations will be submitted for consideration by SAGE to inform the global policy on yellow fever vaccine use, and for subsequent issuance of an updated WHO Position Paper on yellow fever vaccines.
Specifically, the Working Group will be asked to address the following areas, among other, in its review:
To support WHO in the development of evidence-based policy options and strategic recommendations on the use of fractional yellow fever vaccine doses
- To this end, the SAGE WG will prepare an independent evaluation of the scientific and technical evidence via a systematic process. 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
To support WHO in the development of evidence-based policy options and strategic recommendations on one versus two life time doses
- To this end, the SAGE WG will prepare an independent evaluation of the scientific and technical evidence via a systematic process. 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.
Timelines
The SAGE Working Group will be established towards the end of the first trimester of 2026 and is expected to accomplish its tasks first with a focus the use of fractional yellow fever vaccines in the context of reactive and preventive campaigns to be presented to SAGE in October 2026, followed by further deliberations on one versus two life-time doses the conclusions of which will be presented to SAGE in 2027.
A WHO position paper on yellow fever vaccines will be scheduled for publication in 2027.
Mode of work
The working group will mainly meet virtually via Microsoft Teams video conferences. One face-to-face meeting may be convened.
Collective expertise needed in the working group
A broad range of disciplines relevant to:
- public health expertise relevant to yellow fever, particularly in low- and middle-income countries;
- epidemiology of yellow fever;
- infectious disease immunology;
- vaccinology
- immunisation programme planning/management, implementation and monitoring;
- mathematical modelling;
- vaccine safety;
- health economics.
In the selection of the members, consideration shall be given to attaining an adequate distribution of technical expertise, geographical representation and gender balance.
In the selection of the members, consideration shall be given to attaining an adequate distribution of technical expertise, geographical representation and gender balance.
Proposals for nominations should be sent by email to sageexecsec@who.int, along with a curriculum vitae, an indication of relevant expertise, and a completed declaration of interest form. Only complete nominations received by 04 March 2026 will be considered.
Information on the purpose, structure and functioning of SAGE Working Groups is available at: https://www.who.int/groups/strategic-advisory-group-of-experts-on-immunization/working-groups
For more information on SAGE and SAGE working groups:
SAGE and SAGE WG methodologies