On May 7, 2013, the World Health Organization (WHO) announced that the yellow fever ‘booster’ vaccination given ten years after the initial vaccination was not necessary. The WHO’s Strategic Advisory Group of Experts on immunization (SAGE) reviewed the latest evidence and concluded that a single dose of vaccination was sufficient to confer life-long immunity against yellow fever disease.

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.