Mpox vaccine shows promise for teens in new study
NCT ID NCT05740982
First seen Jun 25, 2026 · Last updated Jun 27, 2026 · Updated 1 time
Summary
This study tested the JYNNEOS mpox vaccine in 450 healthy teens and adults to see if it works as well in adolescents aged 12-17 as it does in adults. Participants received two shots under the skin. The main goal was to compare immune responses and check for side effects. Results could help expand vaccine access to younger people.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- MVA-BN (JYNNEOS) vaccine
- What this could lead to
- If successful, this could show that the mpox vaccine is safe and effective for adolescents, helping to protect younger people during outbreaks.
- What could go wrong
- This is a phase 2 trial, so it is still early. The immune response in teens might not match adults, and rare side effects could appear. Results may not apply to all populations.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
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Phase 2
Tests whether the treatment actually works, and watches for side effects, in a larger group.
- Participants
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450 people
The number who actually took part.
- Started
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Mar 2023
- Finished
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Aug 2024
- Lead sponsor
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A government research agency
The lead sponsor is the US National Institutes of Health.
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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12 to 50 years
- 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. Individuals 18 - 50 years of age inclusive at the time of consent; OR Adolescent ages 12 to 17 years inclusive at the time of consent. 2. Adult participant is able to read the written informed consent, states willingness to comply with all study procedures and is anticipated to be available for all study visits; OR Parent(s)/Legal Authorized Representative (LAR)(s) of the participating adolescent is able to read and provides written informed permission and participating adolescent provides assent as appropriate for age or development and approved by IRB. Adolescent states willingness to comply with all study procedures and is anticipated to be available for all study visits. 3. . Adult participant is able to understand and agrees to adhere to Lifestyle Considerations during the study; OR Parent(s)/LAR(s) of the participating adolescent is able to understand and states willingness to comply with Lifestyle Considerations. 4. Females of reproductive potential who have sexual intercourse with males must agree to use highly effective contraception for at least 1 month prior to signing ICF and through Day 57. NOTE: See MOP for definitions and list of acceptable and highly effective methods of contraception 5. In good general health as evidenced by medical history, physical examination, and clinical judgement of the investigator to be in stable state of health. NOTE: Participants with pre-existing stable chronic medical conditions defined as conditions not requiring significant change in therapy or hospitalization for worsening disease in the 4 weeks prior to enrollment can be included at the discretion of the investigator. This includes stable, well-controlled HIV positive individuals. 6. Individuals with HIV must be on suppressive ART for at least 6 months, report a CD4 count of greater than 350 cells/µL and no AIDS-defining illness in the last year. Exclusion Criteria: 1. Ever received a licensed or an investigational smallpox or monkeypox vaccine. \*This includes Dryvax, Acam2000, LC 16 m8, MVA-based vaccine candidate or licensed vaccines, and Jynneos, Imvamune or Imvanex) 2. Any history of monkeypox, cowpox, or vaccinia infection. 3. Close contact of anyone known to have monkeypox in the 3 weeks prior to signing ICF 4. Immunocompromised as determined by the investigator 5. Recent or current use of any immunosuppressing medications in the 4 weeks prior to signing ICF. \*\*Topical, ophthalmic, inhaled, intranasal and intraarticular corticosteroids are acceptable, but receipt of \>/=20 mg/day of prednisone or equivalent for \>/=14 consecutive days in the 4 weeks prior to signing ICF is exclusionary. 6. Pregnant or breast feeding. 7. Received or plans to receive a live vaccine or any COVID-19 vaccine in the 4 weeks before or after each study vaccination. 8. Received or plans to receive any other vaccine in the one week before or after each study vaccination. 9. Received experimental therapeutic agent or vaccine in the 3 months prior to signing ICF. 10. Has known allergy or history of anaphylaxis or other serious adverse reaction to a vaccine or vaccine products. \*\*\*This includes individuals with history of severe allergic reaction to gentamicin, ciprofloxacin, chicken or egg protein. 11. Has tattoos, scars, or other marks which would, in the opinion of the investigator, interfere with assessment of the vaccination site. 12. Has any medical disease or condition that, in the opinion of the participating site PI or appropriate sub-investigator, precludes study participation. \*\*\*\*This includes acute, subacute, intermittent, or chronic medical disease or condition that would place the participant at an unacceptable risk of injury, render the participant unable to meet the requirements of the protocol, or may interfere with the evaluation of responses or the participant's successful completion of this trial. 13. Adolescent or adult participant has a history of myocarditis/pericarditis or a history of structural congenital heart defect/cardiac dysrhythmia that, in the opinion of the investigator, poses increased risk to the participant. 14. Adolescent or adult participant has a history of COVID-19 (with positive test for SARS-CoV-2) in the 4 weeks prior to receipt of the first study vaccination. Note: This includes positive rapid antigen test, polymerase chain reaction (PCR) assay, or other nucleic acid amplification (NAAT) test including those performed by the participant at home.
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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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Baylor College of Medicine
Houston, Texas, 77030-3411, United States
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Brigham and Women's Hospital
Boston, Massachusetts, 02115-6110, United States
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Children's Hospital of Philadelphia
Philadelphia, Pennsylvania, 19146, United States
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Children's of Alabama Child Health Research Unit (CHRU)
Birmingham, Alabama, 35233-0011, United States
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Cincinnati Children's Hospital Medical Center Vaccine Research Center
Cincinnati, Ohio, 45229-3039, United States
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Duke Vaccine and Trials Unit
Durham, North Carolina, 27703, United States
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Emory University School of Medicine
Atlanta, Georgia, 30322-1014, United States
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George Washington University Medical Faculty Associates
Washington D.C., District of Columbia, 20037, United States
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Kaiser Permanente Washington Health Research Institute
Seattle, Washington, 98101-1466, United States
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NIH Clinical Research Center, Investigational Drug Management and Research Section
Bethesda, Maryland, 20892-1504, United States
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Ponce Medical School Foundation Inc., CAIMED Center
Ponce, 00716, Puerto Rico
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Saint Louis University Center for Vaccine Development
St Louis, Missouri, 63104-1015, United States
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UPMC University Center
Pittsburgh, Pennsylvania, 15213, United States
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University of Maryland, School of Medicine, Center for Vaccine Development and Global Health
Baltimore, Maryland, 21201-1509, United States
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University of Rochester Medical Center
Rochester, New York, 14642-0001, United States
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University of Texas Medical Branch
Galveston, Texas, 77555-0435, United States
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Vanderbilt University Medical Center
Nashville, Tennessee, 37212, United States
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Washington University in St. Louis
St Louis, Missouri, 63110-1010, United States
More trials for these conditions
Other studies related to the condition(s) this trial covers.
- Can we better understand mpox in young people?
- Can a smallpox vaccine stop mpox in its tracks?
- Experimental drug targets smallpox and monkeypox after exposure
- Monkeypox vaccine immune response under the microscope
- Can a pill speed up monkeypox recovery? major trial underway
- Scientists investigate mpox in severely weakened immune systems