Background The West Africa Ebola virus disease (EVD) outbreak between 2015 and 2016 accelerated the need for safe and effective vaccines. Among candidate vaccines in clinical development, the recombinant Vesicular stomatitis virus (VSV) vectored with the Ebola virus (EBOV) glycoprotein (rVSV-ZEBOV-GP) vaccine showed acceptable safety and promising immunogenicity results across diverse settings.

Baseline screening data from the phase I trial of this vaccine in Lambaréné, Gabon, established that prior to vaccination about 21% (33/155) and 8% (12/155) of adults had naturally acquired antibodies to infectious ZEBOV particle and ZEBOV-GP, respectively. In participants with prior ZEBOV(-GP) antibodies, post-vaccination antibodies titres were significantly higher 56 days following vaccination with doses of 3×10³, 3×10⁴, and 3×10⁶ PFU compared to those without.

Our study seeks to investigate rVSV vector non-specific boosting of naturally acquired antibodies to other viral infections (dengue virus 1–4, and yellow fever virus).

Methods We measured antibodies titres to Dengue (serotypes 1–4) and yellow fever infection at baseline, 28 and 56 days after injection in a total of 155 serum samples from vaccinees receiving various doses of rVSV-ZEBOV-GP using ELISA technique.

Results Preliminary results were presented at the meeting.

Conclusion Our results confirm rVSV vector non-specific replication on non ZEBOV-GP circulating antibodies in Lambaréné vaccinees and potential boosting action on naturally acquired dengue virus (serotypes 1–4) and yellow fever virus antibodies.