UCSD participating in new monkeypox trial that could stretch vaccine supply

A health worker prepares a dose of monkeypox vaccine.
A health worker prepares a dose of monkeypox vaccine.
(Alain Jocard / Associated Press)

UC San Diego is involved in a new trial getting underway locally and across the nation that aims to further stretch the supply of monkeypox vaccine as demand continues to outstrip supply.

The San Diego County health department said recently that the region had received about 8,000 vials of the vaccine, much fewer than the 33,468 requested. Vaccination clinics are already squeezing up to five doses out of every vial by injecting smaller amounts just under the skin, an “intradermal” technique similar to the one used to administer tuberculosis tests.

Research has indicated that shallow injections do not require a large volume of vaccine because the skin is loaded with specialized immune system cells primed to quickly detect incoming threats from viruses or bacteria.

Though using as little as one-fifth of a vial per recipient is already underway after the federal government approved the practice Aug. 9, experts suspect an even smaller amount — perhaps one-tenth of a vial per person in a two-dose series — might be all that is needed to trigger the body to start producing protective antibodies and other immune system components capable of preventing infection.

UC San Diego is among eight medical providers nationwide set to launch a trial that will compare one-fifth- and one-tenth-size doses of the Jynneos vaccine delivered below the skin with full vials injected at full depth.

“If we can show that they’re all equivalent, we can spread out the available supply of vaccine and administer preventive vaccine doses to more people,” said Dr. Susan Little, an infectious-disease specialist at UCSD who is the trial’s local principal investigator.

UCSD’s Antiviral Research Center has started screening potential participants online at, with doses expected to be given starting this week.

But intradermal vaccination leaves a distinctive raised bump on the forearm after injection, and that mark has come with its own complication, officials said during a monkeypox town hall meeting Sept. 6.

The online event, sponsored by U.S. Reps. Scott Peters (D-La Jolla) and Sara Jacobs (D-San Diego), featured commentary from a range of speakers, including Kim Fountain, deputy chief executive of the San Diego LGBT Community Center. Fountain said the raised bump is causing some to balk at getting the shot.

“These men are terrified of being stigmatized because somebody might see that red spot on them, whether it’s their family or employer or friend, whoever it may be,” Fountain said.

Though anyone can be infected by the monkeypox virus, the current worldwide outbreak has most often affected gay and bisexual men. According to the county health department, 321 cases had been detected locally. Demographic information was available for 313 of them, with 308 listed as men. About 93 percent of those who responded said they are part of the LGBTQ community.

Dr. Davey Smith, an infectious-disease specialist at UCSD who said he has treated many patients with monkeypox infections, confirmed there is concern about any telltale sign that vaccination may leave. Some, he added, have been concerned about the mark that the deeper-injected shot leaves where it is generally administered on the back of the upper arm.

While most monkeypox infections resolve themselves after a few weeks, some experience sore throats so severe that they end up getting admitted to hospitals for narcotic pain medication. The virus also can cause severe constipation that ends up requiring a short hospital stay to resolve, and pox occasionally can appear in private and sensitive locations that end up requiring surgery.

According to the county health department, 10 people across the region had needed hospital stays due to monkeypox. There were no deaths. ◆