The U.S. Food and Drug Administration has approved a freeze-dried formulation of the Jynneos smallpox and mpox vaccine (live, nonreplicating) for the prevention of smallpox and mpox in adults aged 18 years or older.
The approval is intended to support long-term stockpiling efforts by offering improved shelf life, storage, and transportation benefits compared with the currently available liquid-frozen formulation, which was approved in 2019, according to a press release from Bavarian Nordic on March 31, 2025.
The decision followed a standard review of a supplemental Biologics License Application submitted in May 2024, which included clinical data demonstrating comparable immunogenicity and safety between the freeze-dried and liquid-frozen formulations as well as supportive nonclinical and manufacturing data.
The freeze-dried formulation reflects continued efforts between Bavarian Nordic and the U.S. government to enhance preparedness for public health threats. The company has supplied the Jynneos vaccine to the U.S. government for stockpiling since 2010 and initiated manufacturing of the freeze-dried version in 2024 under a contract with the Biomedical Advanced Research and Development Authority (BARDA). Initial deliveries are expected later in 2025.
The Jynneos vaccine is approved for adults at high risk for smallpox or mpox infections, including those who are immunocompromised. The vaccine is the first U.S. Food and Drug Administration–approved nonreplicating smallpox vaccine developed under Project BioShield. In 2022, the U.S. Centers for Disease Control and Prevention (CDC) issued interim guidance for its use during the mpox outbreak, including an Emergency Use Authorization to extend use to patients under 18 years. The CDC updated its recommendations in October 2023 to include routine use in at-risk adults.
Common adverse reactions in vaccine-naive adults included injection site pain (84.9%), redness (60.8%), swelling (51.6%), and systemic symptoms such as muscle pain (42.8%) and headache (34.8%). Similar profiles were observed in previously vaccinated patients, adults with human immunodeficiency virus, and those with atopic dermatitis. Serious adverse events were infrequent and nonfatal. Cardiac adverse events considered causally related occurred in fewer than 0.1% of recipients and were not classified as serious.
This project was supported in part by the U.S. Department of Health and Human Services and BARDA under contract number HHSO100201700019C.