Can anyone have an idea on the scientific basis for the use of the fractional dose (0.1 ml) of Yellow Fever vaccine during a pre-emptive mass vaccination campaign?
As a reminder, in August 2016, the congolese health authorities in collaboration with WHO and CDC launched a preventive mass vaccination campaign against Yellow Fever in Kinshasa and other potentially YF affected provinces. In Kinshasa alone, 7.8 million people were reached in a period of 10 days. As a Vaccinologist I was unable to provide appropriate answer to those asking (and I was asking myself) why a fractional dose was used. From the literature, I know that there is a set lower limit (as per WHO standards) of the amount of viral materials in the 0.5 ml dose, the upper limit is not set. How come that with WHO support, a dose below that set lower limit was given? Was that part of a large scale clinical study at the level of a population in the context of YF vaccine stockout risk? If that's the case, no informed consent was administered and no explanation as such was provided to the vaccinees,is that ethical? Additionally, is it ethical to test a regimen whose efficacy and/or immunogenicity is unproven in a setting of an ongoing outbreak of a dreadful disease? Was the vaccination campaign even needed in the first place to afford that?
Those are questions that trouble me. Your comments and inputs will be very welcome.
Trésor Bodjick Muena Mujobu, MD, MSc