IPM Take
Endemic does not mean harmless. It means the system has lost the luxury of treating prevention as a temporary campaign.
CDC’s latest surveillance analysis suggests clade IIb mpox is becoming a persistent part of the US infectious-disease landscape. That makes the policy failure more visible: vaccination has existed for years, but too many of the people appearing in surveillance data remain unvaccinated.
Executive Summary
CDC analysed 5,322 reported mpox cases in the United States during 2024 and 2025, including 2,803 cases in 2024 and 2,519 in 2025. Persistent low-level transmission across a broad geographic area now suggests a likely transition towards endemic clade IIb circulation.
Among the subset of reported cases with known vaccination status, 76.1% were unvaccinated. In an adjusted analysis limited to 860 patients with the necessary data, unvaccinated patients had 9.73 times the odds of hospitalisationcompared with fully vaccinated patients after controlling for age group and HIV status. The surveillance dataset also has substantial missing information, including vaccination status for most reported cases, which CDC identifies as a limitation.
Why it matters
- Public authorities: Mpox vaccination needs to move from outbreak campaign to durable preventive service.
- Clinicians: Continued low-level transmission means testing and vaccine discussions should remain embedded in routine sexual-health and HIV care.
- Patients and advocates: Persistent racial and ethnic disparities strengthen the case for targeted access strategies rather than passive vaccine availability.
The most politically important word in CDC’s new mpox surveillance report is not “outbreak.” It is “endemic.”
Clade IIb mpox has continued to circulate at relatively low levels in the United States since the dramatic 2022 outbreak receded. The annual numbers no longer resemble the emergency peak, but transmission did not disappear. Cases were geographically widespread in both 2024 and 2025, and infections approximately doubled during September and October 2025 compared with the same period one year earlier before falling back towards baseline.
CDC now says that pattern suggests a likely transition towards endemic circulation. That is not a declaration that mpox has become trivial. It is a warning that temporary emergency programmes are an increasingly poor fit for the epidemiology.
Vaccination is the clearest example. Among cases for which vaccination status was actually available, more than three quarters were unvaccinated. In the adjusted analysis of patients with sufficiently complete data, unvaccinated people had almost ten times the odds of hospitalisation compared with those who had completed the two-dose JYNNEOS series.
That number deserves attention, but also discipline. Vaccination status was missing for a large proportion of reported cases, and the hospitalisation analysis covered only the subset with the necessary information. It should not be transformed into a simplistic claim about national vaccine coverage or absolute individual risk. What it does provide is a strong signal that vaccination remains clinically meaningful even after the sense of emergency has faded.
The harder question is why prevention remains so incomplete. Mpox disproportionately affects gay, bisexual and other men who have sex with men, while Black and Hispanic patients were also disproportionately represented in CDC surveillance. People with HIV face additional risk of severe disease, particularly where immune suppression is poorly controlled. These patterns make passive vaccine availability inadequate. A vaccine can be sitting inside a health department refrigerator and still be inaccessible if the people who need it do not encounter the right service, cannot secure an appointment, are uncertain about eligibility or do not trust the setting offering it.
Endemicity changes the appropriate infrastructure. Mpox vaccination should increasingly sit alongside HIV prevention, PrEP services, STI testing and routine sexual-health care rather than reappearing only when case counts surge. Clinicians need to keep recognising compatible presentations. Public-health teams need genomic surveillance because different clades continue to move internationally. Communities need information that remains specific without sliding back into the stigma that damaged the early response.
There is also a data problem that should not be ignored. CDC’s analysis shows substantial missingness for vaccination status, HIV status, sexual orientation and other variables. A disease cannot be managed precisely when the system does not consistently know who has been vaccinated or which risk factors apply.
The emergency may be ending as a political event. The virus has not agreed to leave with it. That is exactly why the next phase of mpox policy may prove harder than the first: it requires governments to maintain prevention when there is no crisis atmosphere forcing them to pay attention.
