Safety and immunogenicity of mRNA-based mpox vaccine candidate BNT166a: an open-label, dose-escalation, first-in-human trial.
Lancet Infect DisJun 3, 2026 (epub)
Frank Bähner, Saul N Faust, Leela R L Davies et al.
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In 30 seconds
This phase 1 open-label trial evaluated the safety and immunogenicity of the mRNA vaccine candidate BNT166a in healthy adults. Among 64 participants, local reactions were reported in 88% of those receiving the highest dose after the second dose, and binding antibodies were detected in all participants two weeks post-vaccination, persisting for 12 months.
Key findings
- Local reactions were reported in 88% of participants receiving 60 μg BNT166a after the second dose.
- Binding antibodies against all four mRNA-encoded antigens were detected in 100% of participants two weeks post-vaccination.
- 62% to 92% of VACV-naive participants developed MPXV neutralising antibodies depending on the dose.
- 28% of participants experienced BNT166a-related adverse events within 28 days.
Why it matters
The emergence of mpox outbreaks underscores the need for effective vaccines. This study provides initial safety and immunogenicity data for BNT166a, which may inform future vaccine development and public health strategies against monkeypox virus.