Monkeypox virus-neutralising antibodies detected against Clade Ib and Clade IIb in healthy individuals following MVA-BN vaccination

Recently, a novel subclade of mpox virus (MPXV), clade Ib, has emerged in Eastern Democratic Republic of the Congo (DRC). Modified vaccinia Ankara-Bavarian Nordic (MVA-BN) is a third-generation smallpox vaccine that is authorised and in use as a vaccine against mpox. MVA-BN provides approximately 78% protection against disease to Clade IIb MPXV, but there are no data for Clade Ib. We used a plaque reduction neutralisation assay (PRNT) with MPXV clinical isolates from Clade Ib and IIb to investigate immunity in vaccinated health care workers. Here we show that a two-dose regimen of MVA-BN can induce MPXV-neutralising antibodies against both clades, with higher responses to Clade IIb than Clade Ib. KEY POINTS 1. Vaccination with MVA-BN generates antibodies that can neutralise MPXV Clade Ib and IIb. 2. Despite the small sample size paired analysis across the vaccine recipients demonstrate higher neutralisation to Clade IIb than Ib.