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SLU Researchers Begin Enrolling Adolescents in Mpox Vaccine Clinical Trial


Researchers at Saint Louis University’s Center for Vaccine Development are inviting volunteers between the ages of 12-17 and 18-50 to participate in a national clinical trial involving the JYNNEOS mpox, formerly known as monkeypox, vaccine. The trial will evaluate the safety and immune response after two doses of JYNNEOS are administered subcutaneously to adolescents compared to adults.

Dr. Frey sits looks into a microscope while sitting in a scientific lab.

Sharon Frey, M.D., clinical director of the Saint Louis University Center for Vaccine Development and principal investigator of the current trial

The JYNNEOS vaccine, which is the only FDA-approved vaccine for mpox, has a well-known safety profile in adults. The vaccine is currently only licensed for use in adults, and therefore the purpose of this clinical trial is to study whether the licensed dose is safe and elicits immune responses in adolescents that are comparable to those in adults.

The study is sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. SLU’s participation is funded through a contract with Frederick National Laboratory for Cancer Research, operated by Leidos Biomedical Research in Frederick, Maryland, which provides scientific support to NIH. 

“While mpox isn’t as deadly as smallpox, it is a serious illness that causes painful lesions,” said Sharon Frey, M.D., clinical director of the Saint Louis University Center for Vaccine Development and principal investigator of the current trial.

The SLU Vaccine Center will enroll volunteers in the Phase 2 clinical trial. Adolescent participants must be between 12-17 and not have previously received a mpox or smallpox vaccination or had mpox. Participation in the trial may last about 13 months.

“While the initial mpox outbreak has subsided, the odds are good that cases may increase at some point in the future,” Frey said. “Mpox can be spread simply through close contact and also sexual activity. Young people are among those who are at risk and so it’s important that we study the mpox vaccine in this age group.”

Interested participants should contact the Saint Louis University Center for Vaccine Development.

For more information about the trial, visit The study’s Clinical Trials Identifier is NCT05740982.

SLU Center for Vaccine Development

Saint Louis University has been on the front lines in the fight against pandemics and global health crises for more than three decades and first received federal funding for vaccine research in 1989. 

Led by Daniel Hoft, M.D., Ph.D., SLU’s Center for Vaccine Development is one of only 10 institutions selected by the National Institutes of Health as a Vaccine and Treatment Evaluation Unit (VTEU).

As a VTEU, the center helps develop and evaluate vaccines that will protect people from infectious diseases and emerging threats. It conducts Phase 1 through 4 vaccine and treatment trials, including clinical studies in collaboration with industry partners.