Public Health Impact of the MVA-BN Vaccine During the 2022 Mpox Outbreak: A Systematic Review

Previously endemic to sub-Saharan Africa, mpox has since emerged globally, resulting in more than 150,000 cases in over 100 countries in the 2022 outbreak. The Modified Vaccinia Ankara-Bavarian Nordic (MVA-BN) vaccine is licensed and recommended for at-risk populations in many countries and received World Health Organization (WHO) pre-qualification in September 2024.

We conducted this systematic literature review (SLR) to compare analyses, published from 2022 through 2024, of cases averted due to mpox vaccination during the 2022 outbreak to assess the feasibility of estimating the impact on the United States (US). The search included studies that utilized reported case data from any country.

Nine studies were identified. Four estimated the impact of the vaccine as directly modeled in the 2022 outbreak, and cases averted ranged from 10% to 79%. One assessed the projected impact on future outbreaks. Four estimated the impact of hypothetical vaccination strategies. Only one model utilized assumptions appropriate for the US outbreak and population, to allow for an estimate of US cases averted (53,499 cases averted due to the synergistic effects of the vaccine and behavioral changes, with 8096 due to the mpox vaccine alone and 5478 due to behavioral changes alone).

Variation in estimates for the impact of the vaccine can typically be explained by differing model approaches, assumptions, inputs, and epidemic peaks and vaccination campaign roll-out. Most models were not generalizable to the US outbreak and population, but one yielded a reasonable estimate. Nevertheless, all models emphasized the importance of vaccination combined with other public health interventions.