New vaccine trial aims to shield frontline workers from deadly mpox
NCT ID NCT02977715
First seen Jun 27, 2026 · Last updated Jun 27, 2026
Summary
This study tested the JYNNEOS smallpox vaccine in 1,600 healthcare workers in the Democratic Republic of the Congo who are at high risk of catching mpox. The goal was to see if the vaccine can prevent mpox infection and is safe to use. Participants received the vaccine and were monitored for infections, side effects, and immune responses.
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Study facts
What this study's own registry entry says, in plain language.
- Phase
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Phase 3
Large-scale testing in a bigger group. Usually the last step before a treatment can be approved.
- Participants
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1,600 people
The number who actually took part.
- Started
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Feb 2017
- Finished
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Oct 2025
- Lead sponsor
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A government agency
The lead sponsor is a US federal agency other than the NIH.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
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18 years and older
- Sex
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Anyone
- Healthy volunteers
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Accepted
You do not need to have the condition being studied to take part.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
Inclusion Criteria: 1. Males and nonpregnant females (as indicated by a negative urine pregnancy test prior to first dose of vaccine) age 18 years and older. 2. Healthcare personnel at risk of mpox infection working in the Tshuapa Province of DRC or laboratory personnel performing diagnostic testing for mpox at the time of enrollment 3. Willing to adhere to infection control recommendations to the extent possible based on availability of resources. 4. Able and willing to complete the informed consent process and study procedures (including blood sample collection, urine pregnancy test, and completion of adverse event diary and exposure forms). 5. Available for all study visits. Exclusion Criteria: 1. Any history of allergy or anaphylaxis to any prior vaccines, eggs, or aminoglycosides. 2. Current pregnancy (a negative urine pregnancy test is required for women participants who self-report as not pregnant). Enrollment for such participants may be deferred to a later time at which this criteria can be met. 3. Acute illness that is accompanied by an axillary temperature ≥37.2°C (99.0°F) at the time of vaccination. Enrollment for such participants may be deferred to a later time at which this criteria can be met. 4. Known experimental research agents or other vaccine within 28 days (4 weeks) prior to vaccination. Enrollment for such participants may be deferred to a later time at which this criteria can be met. 5. Any reason the PIs suspect that data collected from this person would be incomplete or of poor quality. 6. Any condition that the PIs suspect may place the participant at an unacceptable risk of injury or render the participant unable to meet the requirements of the protocol.
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
Locations
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Tshuapa site
Boende, Tshuapa, Democratic Republic of the Congo