Sunday, May 19, 2013

Yellow Fever Vaccination Boosters: Unnecessary per WHO

Aedes aegypti mosquito (the mosquito that transmits the
yellow fever virus);
Here is a press release from the World Health Organization regarding yellow fever vaccination; this is a 'game changer' for immunization programs in endemic countries as well as for people traveling to endemic areas.

"Yellow fever" refers to the disease caused by the yellow fever virus that is transmitted by mosquitoes in areas of Africa and South America. This a hemorrhagic fever virus associated with substantial mortality and high morbidity. Worldwide there are approximately 200,000 cases yearly with 30,000 deaths. Although a safe and effective vaccine is available for this disease, there is no treatment (other than supportive care) for people who contract it. 

The press release refers to an analysis that was done looking at whether "booster" doses of yellow fever vaccine are needed following initial vaccination. The current practice is to administer a booster dose every 10 years. Yellow fever is (nearly) unique in that it is one of the only vaccine-preventable diseases where there is an international requirement to have documentation of having received the vaccine (or having a medical contraindication) to allow travel to many countries in Africa and South America. The vaccine is generally well tolerated, although it is a live virus vaccine and is contraindicated for people with immune-suppressing conditions. 

The press release noted that over 600 million doses of yellow fever vaccine have been administered since the 1930s when yellow fever vaccination began. There have only been 12 cases of yellow fever following vaccination and these did not occur greater than 10 years following vaccination; all told, the analysis was inconsistent with waning immunity and need for booster immunization. 

This is welcome news, although time will tell how this will effect vaccination programs as well as international travel requirements for yellow fever vaccination. 

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