A comparison of two- and three-dose MVA-BN mpox vaccination series on anti-monkeypox virus immunity

The 2022 global outbreak of clade IIb mpox represented a turning point in public health's handling of poxviruses. The primary vaccine available for the prevention of mpox is modified vaccinia Ankara from Bavarian-Nordic (MVA-BN). We previously reported a nondurable and low-avidity antibody response against mpox elicited by MVA-BN. In this study, we expanded upon this knowledge by employing a microneutralization assay to measure monkeypox virus (MPXV) neutralizing titers and a multiplexed immunoassay to assess IgG titers and avidity against eight MPXV antigens and two vaccinia antigens. Through a machine learning analysis, we uncovered that MVA-BN vaccinees without prior smallpox vaccination largely return to a baseline seroprofile within a year of immunization. Notably, we identified a discrete population within this group that mounted a robust neutralizing antibody response associated with a longer dosing interval during the MVA-BN primary series. Furthermore, we found that boosting with a third dose of MVA-BN increases IgG avidity against certain MPXV antigens, as part of a booster-specific seroprofile. These findings provide critical insights into optimizing immune responses through MVA-BN boosters, presenting a potential approach to addressing the limited MPXV-specific immunity observed following the primary series.