Bavarian Nordic’s Mpox Vaccine Safe, Effective at Lower Doses: Study

Filling Vaccine Syringe/iStock, Kuzmik_A

Pictured: Syringe drawing vaccine from a vial/iStock, Kuzmik_A

A Phase II study funded by the National Institutes of Health found that a dose-sparing, intradermal regimen of Bavarian Nordic’s intradermal mpox vaccine Jynneos (modified vaccinia Ankara-Bavarian Nordic) can match the antibody response elicited by the standard-dose regimen.

The mid-stage results—presented over the weekend at the European Society of Clinical Microbiology and Infectious Diseases Global Congress in Barcelona, Spain—showed that inoculation with one-fifth of the standard Jynneos dose induced an equivalent antibody response two weeks after the second vaccine dose, compared with the standard regimen.

The response waned after two additional weeks, with antibody levels dropping below that in the standard regimen arm. The clinical relevance of this decrease is unknown, according to National Institutes of Health (NIH)’s announcement. Participants who were given one-tenth of the standard dose showed inferior antibody response at all time points.

The dose-sparing regimen was also deemed safe. Adverse events were comparable across all trial arms and the most common side effects were mild injection-site reactions. There were no serious adverse events connected with the vaccine.

The study was supported by the NIH’s National Institute of Allergy and Infectious Diseases. Jynneos is also being studied in adolescents and a readout is expected later this year.

Developed in partnership with the U.S. government, Jynneos is an attenuated live vaccine designed to prime the immune system to fight against orthopoxviruses. The FDA greenlit the vaccine in September 2019, making it the first shot approved for the prevention of smallpox and mpox.

In mid-2022, an mpox outbreak hit the U.S. forcing some states to declare local health emergencies. Bavarian Nordic at the time pledged at least 500,000 additional doses of Jynneos to the federal government, but quickly found that its supply could not keep up with demand.

In August 2022, the company put out a call for help for external assistance to speed up some of its manufacturing processes and hasten production. “It’s no longer certain that we can continue to meet the demand we’re facing even with the upgrade of our existing manufacturing site in Denmark,” Vice President Rolf Sass Sorensen said at the time.

To help meet the overwhelming demand, the FDA allowed the emergency use of Jynneos at one-fifth its standard dose, delivered intradermally.

Earlier this month, Bavarian Nordic launched Jynneos commercially in the U.S. making it more broadly accessible to patients and opening up reimbursement by public and private payers.

Tristan Manalac is an independent science writer based in Metro Manila, Philippines. Reach out to him on LinkedIn or email him at or

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