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SLU is looking for clinical trial participants to test mpox vaccine in adolescents, teens

Dr. Sam Tochtrop holds a small, clear vial of the JYNNEOS monkeypox vaccine while wearing a latex glove.
Sarah Fentem
St. Louis Public Radio
Dr. Sam Tochtrop holds a small vial of mpox vaccine during a vaccination event at Tower Grove Pride in 2022.

St. Louis University is looking for people between 12 and 50 years old to enroll in a clinical trial to see if the mpox vaccine is as effective in people under 18 as it is in adults.

The trial is spurred in part by last year’s outbreak of the virus, which infected more than 200 people in Missouri and thousands more nationwide. Mpox — formerly known as monkeypox — spreads through close contact with an infected person. It causes fever, flu-like illness and trademark lesions.

The safety of the vaccine, also used to prevent smallpox, is well documented for adults, said Dr. Sharon Frey, the clinical director SLU’s Center for Vaccine Development and principal investigator of the mpox trial. But researchers want to know more about its effectiveness.

“What we really don’t have a lot of data on is that antibody response, do they make a really solid antibody response?” she said. “We anticipate the answer to be yes, but we need the data to prove it.”

The standard dose of the JYNNEOS mpox vaccine is fully approved for use in adults. Last year, the Food and Drug Administration approved it for emergency use in minors because of the outbreak. Emergency use authorizations allow clinicians to administer vaccines with more limited data if there is a compelling public interest, like a large-scale outbreak.

Data collected at SLU and elsewhere could help the drug gain full approval could allow the drug to gain full approval. The federal National Institutes of Health is funding the study.

Mpox largely spreads through sexual contact, but young people who are not sexually active can be infected. The disease can be spread by dancing close together, cuddling and sharing clothes or linens, as well as through prolonged respiratory contact.

“The most obvious scenario is if I contract [mpox] and I have a child, the child could sleep in the same bed as me and could get it,” said Nebu Kolenchery, director of communicable disease response at the St. Louis County Department of Public Health. “Even though most of the cases are transmitted during sex, it’s from prolonged exposure and skin-to-skin contact with the lesions that transmits the disease.”

The vaccine also protects against smallpox, and knowing its effectiveness in young people could be vital in the case of a future outbreak, he said.

Frey also noted even young teens can be sexually active.

“We do want to be able to protect people who would be sexually active and have that contact,” she said. “But we also want to be able to protect the people around them.”

The number of daily mpox cases in the U.S. has declined drastically since the 2022 outbreak. The Centers for Disease Control and Prevention is reporting about one case each day.

Last summer, health departments and providers struggled to vaccinate peopleagainst the disease, which was spreading mostly among men who had sex with men.

The SLU Center for Vaccine Research in 2022 found the vaccine could be effective when injected into the skin instead of subcutaneously into layers of fat, which extended the use of vaccine vials about fivefold.

The clinical trial studying use in young people is only looking at the subcutaneous injection’s effectiveness. Researchers say the participants will be involved for a little more than a year.

Those interested in registering for the trial can find more information by emailing the researchers at vaccine@slu.edu

Sarah Fentem is the health reporter at St. Louis Public Radio.