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Could a smaller dose of monkeypox vaccine work just as well?

NCT ID NCT05512949

What the study statuses mean

This study's is highlighted.

Recruitment status, easiest to join first

Recruiting now
This trial is taking on new participants right now.
Not yet recruiting
Registered, but not yet taking participants.
By invitation only
Not open to general applications. Only people the study team invites can take part.
Paused
Paused for now. It may or may not start again.
Ongoing
Running, but no longer taking on new participants.
Completed This study
The trial has finished. Results may not be published yet.
Stopped early
Stopped early, before it reached the end. That can be for many reasons, including safety.
Cancelled
Cancelled before anyone took part.

Expanded access (not trials)

Expanded access
Not a trial. This treatment can be requested outside a study, case by case, for people who qualify.
Expanded access (paused)
Not a trial. The treatment can normally be requested outside a study, but is unavailable right now.
Expanded access (ended)
Not a trial. The treatment could once be requested outside a study, but no longer can.
Approved
The treatment has been approved, so it is available normally rather than through this programme.

When the status isn't known

Details not published
The full record has not been published yet, so there is little to show here.
Status unknown
This status has not been confirmed recently, so it may be out of date.

First seen Jun 26, 2026 · Last updated Jun 27, 2026 · Updated 1 time

Summary

This study tested whether giving a smaller dose of the MVA-BN (JYNNEOS) monkeypox vaccine under the skin works as well as the standard full dose given into the muscle. About 229 healthy adults aged 18 to 50 received either one-fifth or one-tenth of the standard dose under the skin, or the full dose into the muscle. Researchers measured immune responses to see if the lower doses were non-inferior to the standard regimen.

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 vaccine (JYNNEOS)
What this could lead to
If successful, this could show that smaller doses of the monkeypox vaccine given under the skin are just as effective, allowing more people to be vaccinated with the same supply.
What could go wrong
This is a Phase 2 trial with only 229 healthy adults, so results may not apply to everyone. Lower doses might not provide the same level of protection as the standard dose.

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

Phase 2

Tests whether the treatment actually works, and watches for side effects, in a larger group.

Participants

229 people

The number who actually took part.

Started

Sep 2022

Finished

Feb 2025

Lead sponsor

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

18 to 50 years

Sex

Anyone

Healthy volunteers

Accepted

You do not need to have the condition being studied to take part.

Show 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. 2. 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. 3. Agreement to adhere to Lifestyle Considerations during the study. 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. 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. \*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. If HIV infected individual, they must be on suppressive Antiretroviral therapy (ART) for at least 6 months, report a cluster of differentiation 4 (CD4) count of greater than 350 cells/uL and no Acquired Immune Deficiency Syndrome (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, Modified Vaccinia Ankara (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 Informed Consent Form (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 in the 4 weeks prior to signing ICF and 4 weeks after each vaccination. 8. Received or plans to receive any other vaccine in the 2 weeks prior to signing ICF through Day 43. 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 Principal Investigator (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.

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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

  • Baylor College of Medicine

    Houston, Texas, 77030-3411, United States

  • Brigham and Women's Hospital

    Boston, Massachusetts, 02115-6110, United States

  • George Washington University Medical Faculty Associates

    Washington D.C., District of Columbia, 20037, United States

  • NIH Clinical Research Center, Investigational Drug Management and Research Section

    Bethesda, Maryland, 20892-1504, United States

  • Saint Louis University Center for Vaccine Development

    St Louis, Missouri, 63104-1015, United States

  • The Hope Clinic of Emory University

    Decatur, Georgia, 30030, United States

  • University of California, San Diego (UCSD) - Antiviral Research Center (AVRC)

    San Diego, California, 92103-8208, United States

  • Vanderbilt University Medical Center

    Nashville, Tennessee, 37212, United States

More trials for these conditions

Other studies related to the condition(s) this trial covers.