Domingo C, et al. - As infants aged 9–12 months are routinely administered a single dose of vaccine against yellow fever under the Expanded Programme on Immunization, researchers investigated the long-term persistence of neutralizing antibodies to yellow fever virus following routine vaccination in infancy. In this longitudinal cohort study, protective antibodies against yellow fever were measured using a microneutralisation assay in Malian and Ghanaian children vaccinated around age 9 months; these children were followed up for 4·5 years (Mali), or 2·3 and 6·0 years (Ghana). As per findings, children vaccinated as infants show a large decline in yellow fever immunity. They noted a remarkable reduction in seropositivity, especially among the Ghanaian group after only 2·3 years, in comparison with previously reported seroconversion 28 days after vaccination. This indicates a rapid waning of immunity during the early years after infant vaccination arguing for a revision of the single-dose recommendation for this target population in endemic countries. The short duration of immunity in many vaccinees suggests the necessity for booster vaccination to meet the 80% population immunity threshold for the prevention of yellow fever outbreaks.