Clinical trial to evaluate monkeypox vaccine begins

News release

Thursday, September 8, 2022

NIH study evaluates intradermal delivery to expand vaccine supply.

Interested volunteers can visit and search for an ID NCT05512949 for more information about the trial, including a list of sites. Please do not call or email the NIAID News and Science Writing Branch to inquire about enrollment in this trial

A clinical trial evaluating alternative administration strategies for the JYNNEOS monkeypox vaccine to increase the number of available doses has begun to enroll adult volunteers. The study, which will involve more than 200 adults at eight research centers in the US, is sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. JYNNEOS is manufactured by Bavarian Nordic, based in Copenhagen. It is approved by the US Food and Drug Administration for the prevention of smallpox and monkeypox disease in adults 18 years of age and older who have been identified as being at high risk for smallpox or monkeypox infection.

JYNNEOS contains an attenuated orthopoxvirus called modified vaccinia Ankara (MVA), which does not replicate in human cells. It is approved for administration by two subcutaneous (under the skin tissue) injections 28 days apart; however, the FDA recently authorized intradermal (between the layers of skin) administration of the vaccine for adults, expanding the number of people who can be vaccinated with the currently limited amount. This alternative intradermal dosing regimen uses one-fifth of the standard dose used for subcutaneous administration, allowing healthcare providers to administer up to five times the number of vaccine doses per vial of JYNNEOS vaccine. NIH-supported researchers demonstrated in a 2015 publication that intradermal administration of one-fifth of the standard dose elicited an immune response in recipients that was comparable to the subcutaneous administration method.

“To stop the global epidemic of monkeypox and help protect people at risk of infection, we must ensure that we have an adequate supply of monkeypox vaccine,” said NIAID Director Anthony S. Fauci, Ph.D. “NIAID’s trial of JYNNEOS will provide important information on the immunogenicity, safety and tolerability of alternative dosing approaches that would expand the current vaccine offering.”

The Centers for Disease Control and Prevention reported 20,733 cases of monkeypox in the United States as of May 2022. The global outbreak primarily affects men who have sex with men. The virus usually causes painful skin lesions and flu-like symptoms. Serious complications — which are rare in the United States — can include dehydration, bacterial infections, pneumonia, inflammation of the brain, sepsis, eye infections and death. Historically, the virus has been known to be transmitted from person to person through direct contact with skin lesions, body fluids, and respiratory droplets, and through indirect contact with objects such as contaminated clothing or bedding. Preliminary analyzes suggest that sexual transmission may play a role in the current outbreak.

Adults ages 18 to 50 who have not previously been vaccinated against smallpox or monkeypox can enroll in the NIAID study. The researchers aimed to enroll a demographically diverse group of volunteers that represented those affected by monkeypox. All trial participants will receive the JYNNEOS vaccine in some form. Participants will be randomly assigned to one of three study groups:

  • One hand will receive the standard, licensed layout of 1×108 infectious virus particles administered subcutaneously.
  • Another hand will get 2×107 infectious virus particles (one-fifth of the standard regimen) administered intradermally, the regimen recently cleared by the FDA.
  • A third shoulder will receive one tenth (1×107 infectious viral particles) from the standard regimen of JYNNEOS administered intradermally.

The researchers will assess whether the peak immune responses elicited in recipients receiving the vaccine intradermally are at least as good as those elicited by the licensed subcutaneous regimen and will compare the relative safety and tolerability of the different regimens.

Volunteers will be asked to participate in eight study visits over the course of a year, where they will undergo physical examinations and provide blood samples for laboratory evaluations. An independent Data and Safety Monitoring Board (DSMB) will monitor participant safety for the duration of the study.

The trial will involve volunteers at the following sites:

  • Saint Louis University of Missouri
  • Baylor College of Medicine in Houston
  • Brigham and Women’s Hospital in Boston
  • The NIH Clinical Center in Bethesda, Maryland
  • George Washington University in Washington, DC
  • Vanderbilt University in Nashville, Tennessee
  • The Hope Clinic at Emory University in Decatur, Georgia
  • University of California, San Diego

Investigators expect the trial to take 15 months to complete; however, initial results may be available in early 2023. For more information, please visit and search for identifier NCT05512949.

NIAID conducts and supports research—at NIH, in the United States, and around the world—to study the causes of infectious and immune-mediated diseases and to develop better means of preventing, diagnosing, and treating these diseases. News releases, fact sheets, and other materials related to NIAID are available on the NIAID website.

For the National Institutes of Health (NIH):NIH, the national agency for medical research, includes 27 institutes and centers and is part of the US Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research and investigates the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit

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