Safety profile of fractional dosing of the 17DD Yellow Fever Vaccine among males and females: Experience of a community-based pharmacovigilance in Kinshasa, DR Congo.

BACKGROUND: In early 2016, there was a Yellow Fever (YF) outbreak in Central Africa with several deaths reported from Angola and the Democratic Republic of Congo. Due to a shortage in vaccine supply, fractional dosing (0.1 ml) of 17DD Yellow Fever Vaccine (YFV) was proposed in preventive vaccination campaign in Kinshasa in August 2016. A Pharmacovigilance surveillance at community level was implemented to track Adverse Events Following Immunization (AEFIs). The objective of this study was to describe AEFIs as captured from community-based pharmacovigilance and to compare the safety profile of the fractional dosing of YFV between gender.

METHODS: PV information sessions were organized in churches, academic institutions, and pediatrician, obstetrician and friend networks. Prior to data collection, education about AEFI was provided through face-to-face discussions, phone calls, SMS and WhatsApp messages. Individuals reported AEFIs though the above communication channels to assigned individuals. Reported AEFIs were entered into VigiFlow and extracted for statistical analysis using Stata 12. Only vaccinees who received fractional dose (subjects from the age of 2-year-old and non-pregnant women) were included in analysis. Proportional t-test was used to compare AEFI preferred terms among males and females.

RESULTS: A total of 4020 subjects reported 5409 AEFIs. Reporters were mostly males (54.9%) with an average age of 26 ± 10.7 years. Fever and injection site pain were the most reported systemic and local AEFI respectively. The safety profile was similar between gender although females reported more diarrhea and dizziness whilst males reported more asthenia (P < 0.001). Five individuals reported serious AEFIs. Among them, 4 were less-immunocompetent.

CONCLUSION: Fractional dosing of 17DD YFV has a good safety profile, which is similar between gender. These findings complement the documented immunogenicity profile to support recommendation of fractional dose of YFV for outbreak control.