An expert panel of the World Health Organization (WHO) has advised that lowering the dosage of yellow fever vaccine could control an outbreak while avoiding vaccine shortages.
“Fractional dosing of yellow fever vaccine to one fifth of the standard dose (0.1ml instead of 0.5ml) could be a safe and effective option for mass vaccination campaigns to control urban outbreaks in situations of acute vaccine shortage,” says the WHO strategic advisory group of experts (SAGE) on immunisation.
The smaller dose would still provide protection for at least 12 months, SAGE says, but cautions that more research is needed to find out the efficacy of lower doses in young children, who may have a weaker immune response to yellow fever vaccine.
Jon Abramson, chair of SAGE, says: “Given the wide spread of the disease in Angola and the potential for it to get out of control in the city of Kinshasa, in the Democratic Republic of Congo (DRC), WHO and partners are seriously considering the use of this dose-sparing strategy to prevent transmission through large-scale vaccination campaigns.”
By mid-June 2016, WHO and partners had distributed almost 18 million doses of yellow fever in emergency vaccination campaigns in Angola, the DRC and Uganda.
According to the WHO, its response to the Angola outbreak has depleted the global emergency stockpile of 6 million yellow fever doses twice this year already.
Since the outbreak began in December 2015, Angola has reported 3,137 suspected cases and 345 deaths, and the DRC 1,044 cases and 71 deaths.
The WHO says the fractional dosing is under consideration as a short-term measure for use in emergencies and is “not proposed for routine immunisation” and would also “not qualify for a yellow fever certificate” under the International Health Regulation requirements.
“Travellers will need to obtain the full dose of the vaccine,” it concludes.