Yellow Fever had returned as a major scourge and, as urbanization progresses across Africa, the threat of a major epidemic looms ever larger. WHO estimates, for example, that this highly transmissible disease could infect around one-third of an urban population, or up to 4.5 million people, in Lagos, Nigeria alone.

Now, thanks to the $58m GAVI Alliance grant, immunization against Yellow Fever will be kick-started. 

Over the next four years, the world's 12 highest-burden countries, all of which are in West Africa, will be able to implement special vaccination campaigns to immunize more than 48 million people.

"The Initiative is a groundbreaker from many perspectives. Existing routine immunization programmes target children. 

If we were to do only routine child immunization for Yellow Fever, we would need decades to reduce the risk of epidemics and the international spread of the disease," said Dr David Heymann, WHO Assistant Director-General for Communicable Diseases.

"Now, however, thanks to the generous grant from GAVI, the 'Yellow Fever Initiative' will be able to vaccinate at-risk populations and thus quickly reduce the risk of devastating outbreaks that could otherwise threaten the region and the world. 

With this initiative, we will be working in the short- and long-term to strengthen primary health care systems in the world's most vulnerable region - Africa," added Dr Mike Ryan, Director of the WHO Department of Epidemic and Pandemic Alert and Response (EPR) in Geneva.

“Yellow fever is a particularly dangerous disease which kills up to 50 percent of those with severe illness. Every age group is at risk, and vaccination is our crucial weapon to prevent cases and epidemics. With the GAVI Alliance contribution, affected countries have an exceptional opportunity, and responsibility, to protect their populations," said Michel Zaffran, Deputy Executive Secretary at the GAVI Alliance, in announcing the GAVI contribution. 

"GAVI is committed to working with all our partners, both globally and in the field, to ensure the success of the Yellow Fever Initiative in Africa.”

Until now, vaccine has often been too expensive for countries to afford when faced with a host of competing health problems and coverage rates in some West African countries are critically low. 

In Nigeria, for example, the coverage rate in 2005 was an estimated 36%. However, it is recommended that, to stop Yellow Fever infections from spreading into an epidemic, immunization coverage must be at least 60-80%.

"Immunization against Yellow Fever is all the more critical now because of increased population movements in Africa. 

As we see more people moving to cities for work, but returning to their rural villages from time to time, we also see the possibility of Yellow Fever epidemics multiply," said Dr Sylvie Briand, Project Manager of the Yellow Fever Initiative in WHO's EPR Department.

A recent vaccination campaign in Togo has shown how, under the umbrella of the "Yellow Fever Initiative", it is possible to quickly and effectively reach even remote populations and consequently prevent isolated cases from spreading into an epidemic. 

In December 2006, WHO received notification of three cases of Yellow Fever in northern Togo. As the last mass vaccination there had taken place in 1987, the population was considered to be highly susceptible. 

By February 2007, the Togo Ministry of Health and WHO, with financial support from GAVI and from the Humanitarian Office of the European Commission (ECHO), and with the technical support of UNICEF and various NGOs, had vaccinated more than 1.5 million people. 

A similar campaign was then conducted in two districts in southern Togo after two cases of Yellow Fever had been reported there at the end of January.

GAVI's grant to the Yellow Fever Initiative will cover the 12 countries which are at the highest risk from Yellow Fever - Benin, Burkina Faso, Cameroon, Côte d'Ivoire, Ghana, Guinea, Liberia, Mali, Nigeria, Senegal, Sierra Leone and Togo - and will help create a stockpile of 11 million doses of vaccine. 

Within the framework of the Initiative, the 12 Member States and WHO will identify specific target populations to vaccinate, with the aim of both preventing outbreaks and managing epidemics, and consequently increasing immunization coverage.

Yellow Fever is an acute, haemorrhagic, viral disease that is transmitted to humans by infected mosquitoes. 

Infection may result in anywhere from no to severe illness; 20-50% of those with severe illness will die of the disease. 

There is no known specific antiviral therapy, although the disease can be prevented by the "17D" vaccine, which provides immunity for at least 10 years.

Yellow Fever is endemic in tropical regions of Africa and South America, where 44 countries (33 in Africa and 11 in South America) are considered to be at risk. Currently, 610 million people are considered to be at risk from the disease in Africa.

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