BACKGROUND: After months of few mpox cases, an increase in cases was reported in Chicago during May 2023, predominantly among fully vaccinated (FV) 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 the vaccine associated with breakthrough infections. RESULTS: During 18 March-27 June 2023, we identified 49 mpox cases; 57% of these mpox patients were FV. FV patients received both JYNNEOS doses subcutaneously (57%), intradermally (7%), or via heterologous administration (36%). FV patients had more median sex partners (3; interquartile range [IQR] = 1-4) versus not fully vaccinated 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 that 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.

During April 17–May 5, 2023, 13 monkeypox (mpox) cases were reported to the Chicago Department of Public Health (CDPH) after 2 months during which only a single case had been reported. The cluster was remarkable because it comprised more than 10 cases at a time when sporadic cases or small clusters (i.e., involving fewer than three cases) were being reported in the United States, and >69% of the persons in this cluster had received 2 doses of JYNNEOS or 1 dose of ACAM2000 vaccine.* Some cases among persons who received doses of JYNNEOS vaccine are expected to occur based on vaccine effectiveness data (1,2); however, the observed proportion of cases among persons who had received 2 doses of JYNNEOS or 1 dose of ACAM2000 in this cluster was unusual. This increase in cases before large summer events scheduled nationwide and in Chicago raised concerns about possible future case increases. | | On May 9, 2023, CDPH issued a health alert,† urging clinicians to remain vigilant for mpox cases and encouraging vaccination for persons at risk for mpox.§ CDPH and CDC launched an investigation to 1) determine the cluster’s scope and etiology by evaluating patients’ commonalities, JYNNEOS¶ vaccine cold-chain management, whole genome sequencing of clinical samples, and serologic immune response after infections, and to 2) identify important risk factors for mpox exposure to guide prevention efforts. This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy.**

Background: Hepatitis B affects 257 million people worldwide. Mother-to-child hepatitis B virus (HBV) transmission is a preventable cause of substantial morbidity and mortality and poses greatest risk for developing chronic HBV infection. The World Health Organization recommends that all countries institute universal hepatitis B birth dose (HepB BD) vaccination during the first 24 h of life, followed by timely completion of routine immunization. The objective of this analysis was to assess the cost-effectiveness of adding HepB BD vaccination among sub-Saharan African refugee populations where the host country's national immunization policy includes HepB BD. Methods: We performed a cost-effectiveness analysis of three hepatitis B vaccination strategy scenarios for camp-based refugee populations in the African Region (AFR): routine immunization (RI), RI plus universal HepB BD, and RI plus HepB BD only for newborns of hepatitis B surface antigen-positive mothers identified through rapid diagnostic testing (RDT). We focused analyses on refugee populations living in countries that include HepB BD in national immunization schedules: Djibouti, Algeria and Mauritania. We used a decision tree model to estimate costs of vaccination and testing, and costs of life-years lost due to complications of chronic hepatitis B. Results: Compared with RI alone, addition of HepB BD among displaced Somali refugees in Djibouti camps would save 9807 life-years/year, with an incremental cost-effectiveness ratio (ICER) of 0.15 USD (US dollars) per life-year saved. The RI plus HepB BD strategy among Western Saharan refugees in Algerian camps and Malian refugees in Mauritania camps would save 27,108 life-years/year with an ICER of 0.11 USD and 18,417 life-years/year with an ICER of 0.16 USD, respectively. The RI plus RDT-directed HepB BD was less cost-effective than RI plus delivery of universal HepB BD vaccination or RI alone. Conclusions: Based on our model, addition of HepB BD vaccination is very cost-effective among three sub-Saharan refugee populations, using relative life-years saved. This analysis shows the potential benefit of implementing HepB BD vaccination among other camp-based refugee populations as more AFR countries introduce national HepB BD policies.