MVA-BN Vaccine Effectiveness: A Systematic Review of Real-World Evidence in Outbreak Settings

Abstract

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.

Effectiveness and Safety of the MVA–BN Vaccine against Mpox in At-Risk Individuals in the United States (USMVAc)

“…In this study using administrative US healthcare data, high vaccine effectiveness of 89% was observed in the primary analysis among a small cohort of subjects who received full vaccination with two doses relative to a matched sample of unvaccinated subjects considered to be at a similar risk. While the interpretation of these results may be limited by the small sample size, they are consistent with existing US studies of subjects fully vaccinated, including two case-control studies that reported vaccine effectiveness of 66% using a nationwide Epic electronic health record database and 86% using health department case registries from 12 states, and a study conducted in New York State that reported 76% vaccine effectiveness in men diagnosed with mpox compared to negative controls with rectal gonorrhea or primary syphilis [ 13 , 15 , 26 , 27 ], in addition to other recent systematic reviews and meta-analysis of current literature on real-world evidence of MVA–BN vaccine prevention of mpox that reported vaccine effectiveness ranging from 66% to 90% [ 28 , 29 ]. Further, these results align with recent CDC Morbidity and Mortality Weekly Reports that show that breakthrough mpox infections in the US after two doses of the MVA–BN vaccine are rare [ 30 , 31 ].…”