The effectiveness of the modified vaccinia Ankara-Bavarian Nordic (MVA-BN) vaccine has become a subject of significant interest, especially as global efforts continue to combat the spread of mpox. In this real-world study, researchers set out to determine just how effective a single dose of this vaccine could be in preventing infection in at-risk populations.
The researchers used an emulated target trial approach. They evaluated 9803 men who either had a history of sexually transmitted infections (STIs) or were prescribed HIV pre-exposure prophylaxis. The participants were divided into two groups: those who received the MVA-BN vaccine and those who did not. According to Dr. Christine Navarro, one of the lead researchers, “Our primary goal was to ensure that the study was reflective of real-world conditions, rather than idealized trial settings.”
Vaccine Effectiveness Observed
The study’s primary outcome showed that the vaccine was 58% effective in preventing mpox infection. Dr. Navarro noted, “While 58% might seem modest, it’s important to remember that even moderate protection can significantly reduce the spread of infection, especially in high-risk groups.”
The vaccinated group experienced only 0.09 infections per 1000 person-days, compared to 0.20 per 1000 person-days in the unvaccinated group. Sharifa Nasreen, another key researcher, emphasized, “This data reinforces the need for broader vaccine administration among vulnerable populations to help mitigate future outbreaks.”
Public Health Implications
For policymakers, this research underscores the critical role that targeted vaccination campaigns can play in controlling mpox outbreaks. According to Jonathan B. Gubbay, another co-author, “What this study highlights is that timely vaccination, particularly in high-risk groups, is crucial for curbing infection rates. Our results show that even a single dose can have a meaningful impact.”
Sharmistha Mishra, one of the study’s co-authors, also stressed the importance of continued vaccine monitoring and data collection. “We need to keep evaluating vaccine performance over time, especially as mpox evolves and spreads in new regions,” Mishra stated. “Ongoing surveillance is key.”
Future Research Directions
Despite these findings, the researchers acknowledged that further studies are needed to explore the long-term effects of the vaccine and whether booster doses could improve its efficacy. “It’s likely that future research will look into multi-dose regimens or alternative vaccination strategies to maximize protection,” Darrell H. S. Tan, a co-author, commented. “But for now, this is a solid step forward.”
The study concludes that while the MVA-BN vaccine offers moderate protection, it represents a crucial tool in the fight against mpox. As the world continues to grapple with outbreaks, the insights from this study will likely influence public health strategies moving forward.
Citation:
Navarro C, Lau C, Buchan SA, et al. Effectiveness of modified vaccinia Ankara-Bavarian Nordic vaccine against mpox infection: emulation of a target trial. BMJ. 2024;386. doi:10.1136/bmj-2023-078243.
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