London: A single dose of vaccination is sufficient to confer life-long immunity against yellow fever disease, according to World Health Organisation (WHO).The yellow fever `booster` vaccination given ten years after the initial vaccination is not necessary, according to the latest evidence reviewed by the Organisation`s Strategic Advisory Group of Experts on immunisation (SAGE).Since yellow fever vaccination began in the 1930s, only 12 known cases of yellow fever post-vaccination have been identified, after 600 million doses have been dispensed.Evidence showed that among this small number of `vaccine failures`, all cases developed the disease within five years of vaccination.This demonstrates that immunity does not decrease with time, according to an article published in WHO`s Weekly Epidemiological Record (WER)."The conventional guidance has been that the yellow fever vaccination has had to be boosted after ten years," said Dr Helen Rees, chair of SAGE."Looking at really very good evidence, it was quite clear to SAGE that in fact a single dose of yellow fever vaccine is effective. This is extremely important for countries where yellow fever is endemic, because it will allow them to reconsider their vaccine scheduling. It is also important for travellers," Rees said.Yellow fever is an acute viral haemorrhagic disease transmitted by infected mosquitoes that is endemic to 44 countries in tropical areas of Africa and the Americas.Infection with the yellow fever virus causes varying degrees of disease, from mild symptoms to severe illness with bleeding and jaundice and fatal outcomes.
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