WHO

Yellow fever vaccine: a global partnership

Current WHO recommendation for yellow fever control

Vaccination is the single most important measure for preventing yellow fever. Yellow fever vaccine is safe and effective and provide immunity within one week in 95% of those vaccinated. Yellow fever control is based on the prevention of outbreaks, and this can only be achieved if the majority of the population is immunized. A two-pronged strategy is used to achieve this goal.

The first strategy is the inclusion of the yellow fever vaccine in national childhood routine immunization programmes, to be administered at 9 months of age, simultaneously with the measles first dose. However, reaching the desired level of population immunity takes more than 30 years with infant routine immunization only, even with a high coverage. Therefore this strategy needs to be combined with the implementation of mass preventive vaccination campaigns to rapidly increase the population immunity and to protect susceptible older age groups in selected high risk areas.

During YF epidemics, reactive vaccination campaigns are carried out with minimum delay in order to limit the spread of the disease.

The International Coordinating Group mechanism

In 2000, a global shortage of yellow fever vaccines for outbreak response arose from the long lead-time needed to produce the vaccine. Moreover, poor surveillance and reporting mask trends and make the forecasting of vaccine needs especially difficult.

WHO and its partners in the International Coordinating Group (ICG) for Vaccine Provision for Epidemic Meningitis Control are applying the ICG strategy and mechanism for the release and use of yellow fever vaccine.

With vaccine manufacturers as partners in the ICG, a stockpile of 2 million doses reserved for outbreaks response was established. The yellow fever ICG sub-group evaluates request for yellow fever vaccine based on agreed criteria for vaccine provision. If the criteria is fulfilled, doses are released from the stockpile for emergency control of the outbreak.

Global emergency yellow fever vaccine stockpile

The GAVI (Global Alliance for Vaccine and Immunization) support

As demands for the use of the stockpile increased, a joint WHO-UNICEF proposal was successfully presented to the Global Alliance for Vaccine and Immunization (GAVI) Board in 2003 for financing an increased global stockpile of 6 million doses per year for a period of 3 years. In July 2005, GAVI support was extended for an additional year until 2006.

Use of the vaccine stockpile

This mechanism will ensure that all available vaccine stocks are directed to the areas of most urgent need and that adequate supplies are manufactured and stockpiled against future outbreaks. Since the accumulation of the first stockpile in August 2003, the GAVI global vaccine stockpile has been successfully used in the outbreaks of urban yellow fever in Cote d’Ivoire, in Colombia, Liberia, Senegal and Sierra Leone.

Côte d’Ivoire: First urban fever epidemic in over a decade

In September 2001, yellow fever cases were confirmed in five of the ten communes in Abidjan; suspected cases were also reported elsewhere. Urban yellow fever, although very rare, can spread extremely rapidly among a dense urban population, causing many thousands of deaths and very serious humanitarian consequences. Over 3.5 million people live in Abidjan – the commercial capital of Cote d’Ivoire.

WHO, working closely with UNICEF, coordinated the international response team with partners in the Global Outbreak Alert and Response Network. An Operations Centre was established at the WHO office in Abidjan to coordinate activities in epidemiology, the immunization campaign, and vector control. Global reserve stock and delivery of vaccines and supplies were through the yellow fever sub-group of the International Coordinating Group for Emergency Vaccine Provision.

Vaccines and safe injection equipment were provided. The mass campaign immunized 2.9 million persons over a 10 day period.