The US Food and Drug Administration (FDA) has approved the freeze-dried formulation of Bavarian Nordic’s smallpox and mpox vaccine in a move expected to provide flexibility in stockpiling the jab.
Marketed as Jynneos in the US, the vaccine currently exists in a liquid-frozen formulation. These products require a temperature-controlled supply chain that keeps them frozen between production up until being used on a patient.
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Freeze-dried formulations have fewer supply chain limitations, conferring advantages such as easier transportation, storage conditions, and extended shelf life. Freeze drying is a dehydration process to extend its shelf life and molecular stability.
The FDA approved Bavarian Nordic’s new formulation after the vaccine maker demonstrated comparability to the old formulation in terms of immune responses. The freeze-dried formulation is approved for the prevention of smallpox and mpox disease in adults aged 18 years and older.
This included a Phase II trial in 651 healthy volunteers who were given two doses of either the liquid-frozen vaccine or the freeze-dried counterpart. No statistical differences were observed between the groups in immune responses and no serious adverse events were recorded, although the freeze-dried group did have slightly higher local reactions.
Bavarian Nordic also supplied non-clinical and manufacturing to the FDA as part of the supplemental biologics licence application (sBLA) submitted in May 2024.
The US Government has been working closely with Bavarian Nordic to ensure a stockpile of the vaccines is available in the event of a mpox outbreak. The country has been stockpiling since 2010 and ramped up efforts after the 2022-2023 outbreak, where the disease had spread to all 50 states.
Bavarian Nordic is working closely with the US Biomedical Advanced Research and Development Authority (BARDA) to replenish the country’s vaccine stockpile. In 2017, BARDA awarded Bavarian Nordic a contract to develop a freeze-dried version of the vaccine with a longer shelf-life to replace the stockpile. In 2024, a follow-up $156.8m contract was awarded to support these efforts. Bavarian Nordic stated that manufacturing was initiated in 2024, and the first vaccines will be delivered later in 2025.
Bavarian Nordic’s CEO Paul Chaplin said: “Today’s FDA approval represents a significant milestone in our development of this next generation of Jynneos and in our collaborative efforts with the US Government to strengthen public health security.”
For a time, Jynneos was the only FDA-approved vaccine for the prevention of mpox. Emergent BioSolutions’ ACAM2000 then became the second vaccine for the infectious disease, winning FDA approval to prevent mpox in those at high risk of infection in August 2024.
Bavarian Nordic’s product, also known as MVA-BN and Imvanex in other regions, has been a key pillar of fighting the ongoing mpox outbreak in Africa. The biotech has sent more than a million doses of the vaccine to countries experiencing outbreaks and promised further ramp-ups in vaccine production.
The World Health Organization (WHO) has said the mpox outbreak is still a public health emergency, as per a February update. There have been more than 100,000 cases globally in the ongoing outbreak of Clade II mpox. There have been four cases of Clade I mpox in the US, with the most recent two in New Hampshire and New York in February 2025.
