rVSV-ZEBOV vaccination in people with pre-existing immunity to Ebolavirus: an open-label safety and immunogenicity study in Guinean communities affected by Ebola virus disease (l'essai proches).

Thursday 7 November 2024

Watson CH Gsell PS Hall Y Camacho A Riveros X Enwere G Vicari A Nadlaou SD Toure A Sani IM Diallo A Kolie C Duraffour S Ifono K Maomou A Dore K Djidonou HA Bagayoko A Damey PP Camara MN Diallo FB Oumar FT Toure K Diaby ML Sylla L Conde D Kaba IL Tipton T Eggo RM Marks M Roberts CH Strecker T Günther S Keita S Edmunds WJ Carroll MW Henao-Restrepo AM

BMC medicine 2024 Nov 07; 22(1); . doi: 10.1186/s12916-024-03726-z. Epub 2024 11 07

Cohort study Ebola Ebola virus disease Immunogenicity RVSV-ZEBOV Safety Vaccine

Abstract

BACKGROUND: Zaire Ebolavirus disease (EVD) outbreaks can be controlled using rVSV-ZEBOV vaccination and other public health measures. People in high-risk areas may have pre-existing antibodies from asymptomatic Ebolavirus exposure that might affect response to rVSV-ZEBOV. Therefore, we assessed the impact pre-existing immunity had on post-vaccination IgG titre, virus neutralisation, and reactogenicity following vaccination.

METHODS: In this prospective cohort study, 2115 consenting close contacts ("proches") of EVD survivors were recruited. Proches were vaccinated with rVSV-ZEBOV and followed up for 28 days for safety and immunogenicity. Anti-GP IgG titre at baseline and day 28 was assessed by ELISA. Samples from a representative subset were evaluated using live virus neutralisation.

RESULTS: Ten percent were seropositive at baseline. At day 28, IgG in baseline seronegative (GMT 0.106 IU/ml, 95% CI: 0.100 to 0.113) and seropositive (GMT 0.237 IU/ml, 0.210 to 0.267) participants significantly increased from baseline (both p 0.0001). There was strong correlation between antibody titres and virus neutralisation in day 28 samples (Spearman's rho 0.75). Vaccinees with baseline IgG antibodies against Zaire Ebolavirus had similar safety profiles to those without detectable antibodies (63.6% vs 66.1% adults experienced any adverse event; 49.1% vs 60.9% in children), with almost all adverse events graded as mild. No serious adverse events were attributed to vaccination. No EVD survivors tested positive for Ebolavirus by RT-PCR.

CONCLUSIONS: These data add further evidence of rVSV-ZEBOV safety and immunogenicity, including in people with pre-existing antibodies from suspected natural ZEBOV infection whose state does not blunt rVSV-ZEBOV immune response. Pre-vaccination serological screening is not required.

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