Fractional Dosing of Yellow Fever Vaccine to Extend Supply: A Modeling Study

Wu, Joseph T.; Peak, Corey M.; Leung, Gabriel M.; Lipsitch, Marc

There is a safe, highly effective live-attenuated vaccine against YF. 3 However, the global emergency stockpile of YF vaccines, which has been maintained at approximately 6·8 million doses before 2016, has already been depleted twice by the Angola outbreak. With a throughput of only 2 to 4 million doses per month, YF vaccine supply is inadequate given the large urban populations at risk for YF infection. In response to such shortage, dose fractionation has been proposed to maximize the public health benefit of the available YF vaccines. 4 Under dose fractionation, a smaller amount of antigen would be used per dose in order to increase the number of persons who can be vaccinated with a given quantity of vaccine. 3 This strategy was previously proposed to extend pre-pandemic influenza vaccine supplies. 5 If dose fractionation were consistently adopted, equity of YF vaccine access would also be enhanced both within and across countries at risk, as more people could benefit from vaccination without depriving others. 6 Indeed, following the SAGE endorsement on 17 June 2016, the WHO recommended dose fractionation in its emergency YF vaccination campaign in July-August 2016 to vaccinate 8 million people in Kinshasa, 3 million in anterior Angola and 4·3 million along the DRC-Angola corridor. 7 Specifically, 2·5 million standard-dose vaccines would be allocated to Kinshasa where 200,000 standard-dose vaccines would be given to children age 9 months to 2 years and the remaining allocation are to be fractionated five-fold and administered to the rest of the population.