MVA-BN Vaccine Effectiveness: A Systematic Review of Real-World Evidence in Outbreak Settings
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Background
Mpox is a disease endemic to Central and West Africa. It caused outbreaks in non-endemic countries, mainly in 2022. The endemic Democratic Republic of Congo is currently experiencing its largest outbreak yet. The vaccine Modified Vaccinia Ankara-Bavarian Nordic (MVA-BN) is approved for active immunization against mpox and smallpox. Since the outbreak in 2022, real-world studies have assessed MVA-BN’s vaccine effectiveness (VE) against mpox, and this systematic literature review aims to summarize the most current evidence.
Methods
Medline (via PubMed), Embase, and LILACS were searched, as well as grey literature sources and publications’ bibliographies to identify observational studies published between 1/Jan/2022 and 28/Feb/2024 that estimate the VE of MVA-BN against symptomatic mpox or provide risk measures that allow calculation of these VE estimates. Data were presented descriptively in tables and text; the methodological quality of included records was assessed using an informal qualitative approach.
Results
The literature search identified a total of 16 records that fit the inclusion criteria. The studies took place in high-income countries and were heterogenous in design, setting, and definition of at-risk populations. MVA-BN VE estimates against symptomatic mpox infection ≥14 days post-vaccination were assessed. Where the study population was exclusively or primarily those receiving pre-exposure prophylactic vaccination, the adjusted VE estimates ranged from 35% to 86% (n=8 studies) for one dose and from 66% to 90% (n=5) for two doses. Where only post-exposure prophylactic vaccination was assessed, adjusted VE estimates were reported for one dose only at 78% and 89% (n=2). Additionally, MVA-BN reduced the risk of mpox-related hospitalization in one study and the severity of mpox clinical manifestations in two studies.
Conclusions
Despite heterogeneity in study design, setting, and at-risk populations, the reported VE estimates against symptomatic mpox infection for one or two doses of MVA-BN support deployment of MVA-BN for mpox outbreak control.
