Yellow Fever

Fractional doses: YF vaccine

In July 2016, the demand for yellow fever (YF) vaccines was larger than the available global supply. In this situation, the WHO developed recommendations for the use of fractional doses of YF vaccine as a dose-sparing strategy. Although YF vaccine is highly effective, the current supply shortages constrain vaccination activities, and particularly outbreak response. The yellow fever studies aim to provide additional information on the use of fractional doses.

YEFE

 The aim of this study is to generate the data needed to recommend fractional doses of any WHO prequalified YF vaccine to be used in emergency situations when there are insufficient standard doses to protect the population at risk. The priority is to determine if a fraction of a vaccine dose (i.e. 1/5th) administered subcutaneously would be safe and immunogenic. We designed a double-blinded randomized controlled trial to assess the immunological non-inferiority and safety of a fractional dose compared to full dose for each of the four WHO pre-qualified YF vaccines in an adult population. Each vaccine was delivered in either its full dose or fractional dose. The study included an adult population, children and HIV infected adults.

Country

Uganda, Kenya

Status

Recruitment and follow-up completed

Publication on adult population

Our Role

Sponsor, Scientific Oversight, Study site

NIFTY

The purpose of this study, is to determine the safety and immune response elicited by reduced doses of yellow fever vaccine in comparison to standard dose. This study is a parallel group, randomized, controlled, blinded, noninferiority trial of four different doses of YF vaccine. participants are randomized for vaccination with full standard dose or with 1000, 500 or 250 IU. The primary objective is to determine the lowest dose (1000, 500 and 250 IU/dose) of YF vaccine that is non-inferior to the full standard dose as measured by seroconversion using the PRNT50 assay at 28 days post-vaccination in an adult population.

Country

Uganda, Kenya

Status

Follow-up ongoing

Tentative End date

January 2023

Our Role

Scientific Oversight, Study Site