Background After months of few mpox cases, an increased number of cases were reported in Chicago during May 2023; predominantly among fully vaccinated patients. We investigated the outbreak scope, differences between vaccinated and unvaccinated patients, and hypotheses for monkeypox virus (MPXV) infection after vaccination. Methods We interviewed patients and reviewed medical records to assess demographic, behavioral, and clinical characteristics, mpox vaccine status, and vaccine administration routes. We evaluated serum antibody levels after infection and compared patient viral genomes with MPXV sequences in available databases. We discussed potential vaccine compromise with partners who manufactured, handled, and administered vaccine associated with breakthrough infections. Results During March 18–June 27, 2023, we identified 49 mpox cases; 57% of these mpox patients were fully vaccinated (FV). FV patients received both JYNNEOS doses subcutaneously (57%), intradermally (7%), or via heterologous administration (36%). FV patients had more median sex partners (3, IQR=1-4) versus not fully vaccinated (NFV) patients (1, IQR=1-2). Thirty-six of 37 sequenced specimens belonged to lineage B.1.20 of clade IIb MPXV, which did not demonstrate any amino acid changes relative to B.1, the predominant lineage from May 2022. Vaccinated patients demonstrated expected humoral antibody responses; none were hospitalized. No vaccine storage excursions were identified. Approximately 63% of people at risk for mpox in Chicago were FV during this period. Conclusions Our investigation indicated cases were likely due to frequent behaviors associated with mpox transmission, even with relatively high vaccine effectiveness and vaccine coverage. Cases after vaccination might occur in similar populations.

中文翻译：

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对伊利诺伊州芝加哥影响许多疫苗接种者的MPOX疫情的调查——2023年3月至2023年6月

背景 经过几个月的少数 MPOX 病例后，2023 年 5 月，芝加哥报告的病例数量有所增加；主要发生在完全接种疫苗的患者中。我们调查了暴发范围、接种疫苗和未接种疫苗的患者之间的差异，以及接种疫苗后猴痘病毒（MPXV）感染的假设。方法 我们采访了患者并审查了病历，以评估人口统计、行为和临床特征、mpox 疫苗状态和疫苗接种途径。我们评估了感染后的血清抗体水平，并将患者病毒基因组与可用数据库中的 MPXV 序列进行了比较。我们与制造、处理和管理与突破性感染相关的疫苗的合作伙伴讨论了潜在的疫苗妥协。结果 2023年3月18日至6月27日期间，我们发现了49例mpox病例； 57% 的 MPOX 患者已完全接种疫苗 (FV)。 FV 患者通过皮下注射 (57%)、皮内注射 (7%) 或通过异源给药 (36%) 接受两种 JYNNEOS 剂量。与未完全接种疫苗 (NFV) 的患者 (1，IQR=1-2) 相比，FV 患者的中位性伴侣数量较多 (3，IQR=1-4)。 37 个测序样本中的 36 个属于 IIb MPXV 进化枝的 B.1.20 谱系，与 2022 年 5 月以来的主要谱系 B.1 相比，该谱系没有表现出任何氨基酸变化。接种疫苗的患者表现出预期的体液抗体反应；无人住院。未发现疫苗储存异常。在此期间，芝加哥大约 63% 有 MPOX 风险的人患有 FV。结论 我们的调查表明，即使疫苗有效性和疫苗覆盖率相对较高，病例也可能是由于与 MPOX 传播相关的频繁行为造成的。接种疫苗后的病例可能会发生在类似人群中。