Yellow fever is a viral disease that is transmitted by infected mosquitos. It is mainly found in tropical areas in Africa and South America. Although the current yellow fever vaccine is highly effective with a single dose, vaccine supply is limited.
When outbreaks happen during vaccine shortages, the World Health Organization recommend using a lower dose, but there is currently a lack of research on how effective it is at causing an immune response.
The team at KEMRI Wellcome Trust Research Programme conducted a randomised, double-blind trial in Uganda and Kenya, using 480 volunteers without a prior history of yellow fever or the vaccine. The main goal was seroconversion 28 days after receiving the vaccination, with each of the three smaller doses. The results showed that a dose as low as 500 IU was noninferior, compared to the standard dose of 13,803, regarding the goal of seroconversion at 28 days after vaccination.