As concerns about monkeypox (Mpox) escalate, a recent Phase 2 clinical trial has demonstrated that the Modified Vaccinia Ankara-Bavarian Nordic (MVA-BN) vaccine is safe and immunogenic for adolescents aged 12-17. With children under 15 accounting for 70% of Mpox cases and 88% of deaths in the Democratic Republic of Congo (DRC), this study is particularly timely.
This study was presented at IDWeek, and co-author C. Buddy Creech, MD, MPH, discussed with Contagion the rationale for focusing on adolescents aged 12-17, highlighting the significant impact of Mpox on younger children in the DRC, âWe recognize that this is not just a disease of adults with risk factors; itâs a disease in children too. In our study, we were already conducting an adult study where we compared the regular dose to one that we would administer just at the surface of the skin, just underneath the dermis, or inside the dermis.â He continued, âThe most important piece is that the amount of antibodies that the teenagers produced in response to this vaccine was, if anything, slightly higher than that of adults, which gives us a lot of confidence moving forward. We looked at this in kids aged 12 to 17 years. They were healthy kids. We enrolled them, gave them the doses of vaccine, and then measured their immune response to the vaccine as well as any symptoms they might experience afterward.â
The study compared the immune responses of 315 adolescents to 211 adults aged 18-50, administering two subcutaneous doses of the vaccine 28 days apart. Key findings from the interim analysis indicated that both groups experienced similar rates of solicited systemic and local events, as well as unsolicited adverse events (AEs). Dizziness was reported by 3% of adolescents, with none in adults, aligning with trends observed in other adolescent vaccinations. Overall, the MVA-BN vaccine demonstrated good tolerance among participants. MVA-BN is currently licensed in the US for smallpox and Mpox but is not approved for those under 18, though it is available under emergency use in some countries.
Creech shared insights on the safety profile observed in adolescents compared to adults, particularly regarding dizziness, and how that may shape vaccination recommendations, âDizziness stood out to us because we had about nine events in eight kids, but again, it aligns with what we see with other vaccines in this field. It’s just that teenagers can be a little emotional and anxious about vaccinations, which sometimes leads to that feeling of dizziness.â
Immunogenicity results were promising, with the geometric mean titer (GMT) for adolescents at Day 43 reaching 470.3 (95% CI: 422.3, 523.8), surpassing the adult response of 293.2 (95% CI: 249.8, 344.2) and achieving a GMT ratio of 1.6 (95% CI: 1.32, 1.95).
Creech discussed the next steps for researching the MVA-BN vaccineâs efficacy in younger children, and how do you plan to address the need for their protection, âWhat we need to do next, and what we are doing next, is optimizing the testing in the laboratory to look for very specific Mpox responses, because those assays are actuallyâor those tests are actually harder to do, so we’re working on that right now. But the more important issue is a vaccine is only as good as the public policies around getting those vaccines to those in need.â
In conclusion, the interim data support the safety and effectiveness of the MVA-BN vaccine in adolescents, meeting established non-inferiority criteria compared to adults. These findings underscore the need for vaccination in endemic regions, as well as the necessity for further evaluations in younger children to protect this vulnerable demographic against Mpox. Continued research is essential to fully assess the vaccineâs safety and efficacy across age groups, as Mpox remains a global public health threat.
