As an mpox outbreak in Africa continues to spread, the FDA has approved an Emergent BioSolutions vaccine for preventing infection from this pathogen. The regulatory decision could be the first of several for this vaccine, which is also being discussed with health authorities around the world.
The vaccine, ACAM2000, was initially developed to protect against smallpox. Mpox is a member of the same family of viruses as smallpox. Using a live version of vaccinia, a virus that is related to smallpox but causes milder disease, ACAM2000 is intended to spark the immune system to produce protective antibodies. The FDA approval of the vaccine announced late Thursday covers the prevention of disease in those at high risk for mpox infection.
ACAM2000 is one of two FDA-approved mpox vaccines. In 2019, the regulator approved Bavarian Nordic’s Jynneos for protecting against both smallpox and mpox. Like ACAM2000, Jynneos employs live vaccinia virus. Gaithersburg, Maryland-based Emergent won FDA approval for ACAM2000 in 2007 for protection against smallpox. Though naturally occurring smallpox virus has been eradicated, engineered versions of the virus pose a biowarfare or bioterrorism threat. ACAM2000 was designated for use in the event of a such emergency; it’s stockpiled by the U.S. government and other governments around the world.
During the mpox outbreak two years ago, the FDA broadened the permitted use of the Emergent vaccine to mpox under an expanded access investigational new drug application, which allows the use of an investigational product outside of a clinical trial. The latest regulatory decision for ACAM2000 is an approval of an Emergent supplemental biologics license application submitted to the FDA last fall. The application was based on previously available human safety data and data from a well-controlled animal study that showed ACAM2000 was effective in protecting against mpox virus exposure. The product’s label carries a black box warning regarding the risk of myocarditis (inflammation of heart muscle) and pericarditis (inflammation of the saclike tissue surrounding the heart).
“This expanded indication for ACAM2000 comes at a critical time as the global health community comes together to ensure an effective and cohesive response to the recent upsurge in mpox cases,” Emergent President and CEO Joe Papa said in a prepared statement. “We believe Emergent is poised to support the global response needed by actively engaging with world health leaders, as well as deploying product currently available in inventory based on the needs, as well as the ability to increase supply.”
The 2022 mpox outbreak involved clade II mpox. The public health emergency of international concern for this outbreak concluded in May 2023, following a sustained decline in the number of cases. The current outbreak is caused by the clade I variant, which leads to more severe outcomes, including a higher risk of death. On Aug. 14, the World Health Organization’s (WHO) director-general declared the current mpox outbreak a public health emergency of international concern given its spread in the eastern part of the Democratic Republic of the Congo and its detection in neighboring countries. According to the Centers for Disease Control and Prevention, there have been no clade I mpox cases reported in the U.S. and the risk to the U.S. posed by the current outbreak is low.
Emergent has filed an Expression of Interest with the WHO to assess ACAM2000 for potential Emergency Use Listing, which could expedite availability of the vaccine during an emergency. The company said it is also in discussion with other global public health leaders regarding the mpox outbreak. Emergent said it will donate 50,000 doses of ACACM2000 for potential deployment in Central Africa.
Public domain image by the National Institute of Allergy and Infectious Diseases (NIAID)
