CDC is updating webpages with the term "mpox" to reduce stigma and other issues associated with prior terminology. This change is aligned with the recent World Health Organization decision.

Rates of Monkeypox Cases by Vaccination Status

  • This page displays overall weekly rates of monkeypox cases 
    • among males ages 18 through 49 who were eligible for vaccination 
    • by their vaccination status (vaccinated or not vaccinated), and 
    • by date of illness onset.  

Monitoring monkeypox rates by vaccination status may suggest how well the vaccine is performing in the real-world setting. Rates are not adjusted for time since vaccination, underlying medical conditions (such as HIV status), or other factors.  

To monitor rates of monkeypox cases by vaccination status, jurisdictions report data that identify vaccination status either through case interviews or by linking case surveillance data to immunization registries, and separately submit de-identified vaccine administration data to CDC. 

JYNNEOS is the vaccine being used in the U.S. during this outbreak. U.S. vaccine distribution of JYNNEOS vaccine began in May 2022. Effectiveness and duration of immunity after a single dose is not known, and vaccine effectiveness is anticipated to be greater after two doses. As of September 28, 2022, most vaccine has been administered as post-exposure prophylaxis, and relatively few individuals in the current outbreak have completed the recommended 2-dose series.  

Summary

  • Among 32 U.S. jurisdictions, monkeypox incidence among people who are currently recommended to receive vaccine was higher among unvaccinated people compared with those who had received their first vaccine dose 14 days or more earlier.
  • Several factors likely affect crude case rates by vaccination status. Limitations include the inability to account for possible differences in testing or behaviors between vaccinated and unvaccinated people or possible differences in risk due to patient characteristics such as age or underlying condition status.

Unvaccinated people had:

14 times the risk of monkeypox disease compared to people who were vaccinated*

Rates of Monkeypox Cases by 1st Dose Vaccination Status

July 31, 2022 – September 3, 2022 (32 U.S. jurisdictions)

Source: CDC Multi-National Monkeypox Response 2022, Vaccine Task Force, Vaccine Effectiveness Team

These data were posted on September 28, 2022 and reflect confirmed and probable monkeypox cases with illness onset between July 31, 2022 through September 3, 2022. These data will be updated periodically. Please note that these provisional data are subject to change.
*Vaccination Status: Unvaccinated: no evidence in case record of receipt of vaccine or vaccination date after illness onset, including records where vaccination information was unknown; vaccinated, illness onset 14 days or more after first dose: illness onset 14 days or more after receiving first dose of vaccine, excluding people vaccinated for smallpox before 2022. Linkage of monkeypox case surveillance and vaccination administration data might have resulted in misclassifications.

Population: The population aged 18-49 years eligible for vaccination is derived from the estimated size of the underlying population in each jurisdiction that might benefit from expanded vaccination in the context of the outbreak and includes  gay, bisexual, and other men who have sex with men (MSM) with HIV or who are eligible for HIV preexposure prophylaxis (HIV-PrEP), according to Phase 4 of the National Monkeypox Vaccine Strategy (Administration for Strategic Preparedness & Response). To estimate the number of MSM with HIV, jurisdiction-specific estimates of the prevalence of HIV in 2020 from CDC Atlas Plus describing MSM who acquired HIV from the following transmission categories: “male-to-male sexual contact” and also “male-to-male sexual contact and injection drug use” were used. To estimate the number of MSM who are HIV-PrEP-eligible, the number of people in each jurisdiction prescribed HIV-PrEP, HIV-PrEP coverage in each jurisdiction, the percent of people on HIV-PrEP who are men nationally, the national HIV-PrEP coverage among MSM, and the national HIV-PrEP coverage among men and women from CDC Atlas Plus were combined. The number of MSM with HIV or who are eligible for HIV-PrEP aged 18–49 years was estimated by aggregating 2021 U.S. Census Bureau estimates for males aged 0–12, 13–17, 18–49, and ≥50 years, calculating the state proportion in each age group, and multiplying by the estimated number of MSM with HIV or who are eligible for HIV-PrEP in each state to obtain proportional distributions.

Monkeypox Case: A confirmed case of monkeypox is defined by presence of Monkeypox virus DNA by polymerase chain reaction (PCR) testing or Next-Generation sequencing of a clinical specimen OR isolation of Monkeypox virus in culture from a clinical specimen. A probable case is defined by presence of Orthopoxvirus DNA by PCR, or Orthopoxvirus using immunohistochemical or electron microscopy or detectable levels of anti-Orthopoxvirus IgM antibody.

Participating jurisdictions: Currently, the following 32 health departments identify vaccination status through case interview or link case surveillance data to their own immunization registries and separately submit de-identified vaccine administration data to CDC and are included in these incidence rate estimates: Alaska, California, Colorado, Georgia, Hawaii, Idaho, Illinois, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Missouri, Montana, Nevada, New Hampshire, New Mexico, North Dakota, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Utah, Virginia, West Virginia, and Wisconsin. The data assessed from 32 jurisdictions accounted for 54% of the U.S. population eligible for vaccination, and therefore might not be generalizable.

Illness Onset: Illness onset date refers to the earliest date available for a case. The selection of illness onset dates varied by how the case was reported into the system and may have been dates of any of the following (listed in order by priority and availability): illness onset, specimen collection, lab test completion, admission, diagnosis, discharge, initiation of case investigation, or first electronic submission, or report to the county, state, or public health department. 

Incidence rate estimates: Weekly incidence measures were calculated by vaccination status as the number of cases divided by the number of people either unvaccinated as of that week or vaccinated 14 days or more prior to that week.

Incidence rate ratios (IRR): The average incidence rate ratio (IRR) during the study period was calculated by dividing the weighted average incidence across all weeks among unvaccinated people by that among vaccinated people.

PublicationsPayne AB, Ray LC, Kugeler KJ, Fothergill A, White EB, Canning M, et al. Incidence of Monkeypox Among Unvaccinated Persons Compared with Persons Receiving ≥1 JYNNEOS Vaccine Dose — 32 U.S. Jurisdictions, July 31–September 3, 2022. MMWR Morb Mortal Wkly Rep. ePub: 30 September 2022. DOI: http://dx.doi.org/10.15585/mmwr.mm7140e3.