Authors
Yin-Chien Lin, Tzai-Hung Wen, Wei-Liang Shih, Chia-Wei Liao, Sten H Vermund, Chi-Tai Fang
Published in
BMJ global health. Volume 11. Issue 8. Aug 20, 2026. Epub Aug 20, 2026.
Abstract
The 2022 global mpox epidemic declined before modified Vaccinia Ankara-Bavarian Nordic (MVA-BN) vaccines were widely deployed, contributing to the perception that transmission was self-limiting within a small high-risk population. This may have delayed global vaccine allocation and weakened responses to the resurgence that has disproportionately affected Africa since 2024. The reasons for the 2022 decline remain uncertain, and prior studies have reported widely divergent estimates of vaccination impact. We systematically reviewed and meta-analysed the evolving transmissibility of mpox clades and the effects of interventions.
We searched GenBank, PubMed and Embase through 18 May 2025, for mpox virus sequences, reproduction number (R) estimates and modelling studies evaluating intervention effectiveness. Two reviewers independently assessed eligibility, extracted data and evaluated risk of bias using a validated tool. Random-effects meta-analyses were performed.
Fifty-two studies reporting R estimates and 40 studies evaluating intervention effectiveness met eligibility criteria. For clade I mpox, pooled R increased from 0.71 (95% CI 0.26 to 1.17) during 1970-2017 to 1.23 (1.12-1.33) for subclades Ib/Ia after 2023 (p=0.0303). For clade II mpox, pooled R was 1.11 (0.90-1.32) during 2017-2021 and increased to 2.66 (2.31-3.00) for subclade IIb in 2022-2023 (p<0.0001). During the 2022 subclade IIb outbreak, empirical modelling studies estimated that behaviour change and vaccination together were associated with a substantial reduction in mpox cases (55%, 95% CI 37 to 73; I²=81.2%), although effect sizes varied across settings according to the extent of behaviour change and the timing and coverage of vaccine rollout.
Behaviour change and vaccination likely played important roles in the decline of the 2022 mpox epidemic in many studied settings. Given the stepwise increase in human-to-human transmissibility associated with the emergence of new subclades, effective mpox epidemic control requires proactive, rapid and equitable vaccine rollout supported by culturally tailored risk communication.
CRD420250653072.
PMID:
42624639
Bibliographic data and abstract were imported from PubMed on 21 Aug 2026.
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