As the mpox outbreak continues to escalate in Africa, the U.S. Food and Drug Administration (FDA) has granted approval to Emergent BioSolutions’ vaccine, ACAM2000, aiming to prevent infection from the virus. This approval is a significant move by the FDA and might pave the way for further authorizations as the vaccine is considered by other health authorities worldwide.
Originally developed for smallpox, ACAM2000 leverages a live vaccinia virus, which is closely related to but less harmful than smallpox, to stimulate the immune system to produce antibodies against the disease. The decision to approve the vaccine specifically for mpox, announced by the FDA, is an expansion based on its pre-existing authorization for smallpox prevention in individuals at high risk for mpox infection.
ACAM2000 is not the only vaccine for mpox available on the market; the FDA had previously cleared Bavarian Nordic’s Jynneos in 2019, which also uses a live vaccinia virus and provides protection against both smallpox and mpox. Jynneos and ACAM2000 differ in their development and composition, but each plays a critical role in combating these viral diseases. ACAM2000 was initially approved by the FDA in 2007 to guard against smallpox, in response to concerns about potential biowarfare or bioterrorism involving engineered versions of the virus. Since then, it has been stocked by the U.S. and other governments worldwide for emergency use in such scenarios.
The need to permit ACAM2000’s use against mpox arose during an outbreak two years ago, under an expedited FDA mechanism that allowed its deployment outside clinical trials. The recent regulatory approval stems from Emergent BioSolutions’ submission of a supplemental biologics license application last fall, supported by existing human safety data and results from an effective animal study indicating the vaccine’s efficacy against mpox. Nonetheless, its use comes with a serious caution, as highlighted by a black box warning on its label about potential risks such as myocarditis and pericarditis.
The timing of this approval is crucial according to Joe Papa, Emergent’s President and CEO, as it aligns with a collective international effort to tackle the recent surge in mpox cases. Emergent is prepared to meet the global demand, able to dispatch existing supplies and scale up production as needed.
The recent strains of mpox causing the outbreaks have been identified as clade II in 2022 and the more severe clade I in the ongoing outbreak. The outbreak of clade I mpox has been particularly alarming, prompting the World Health Organization (WHO) to declare it a public health emergency of international concern, especially given its spread in Eastern Democratic Republic of the Congo and detection in neighboring countries. Although this variant poses a greater risk of severe outcomes and mortality, there have been no cases of clade I mpox reported in the U.S., and the threat to the U.S. remains low.
In response to the current situation, Emergent has submitted an Expression of Interest to the WHO for Emergency Use Listing of ACAM2000, which could fast-track its availability in emergency situations. Moreover, Emergent is actively discussing with global health leaders ways to tackle the mpox challenge and has pledged to donate 50,000 doses to possibly be used in Central Africa, underlining its commitment to supporting global health during this crisis. This move underscores the broader strategy and readiness of health authorities and pharmaceutical companies to respond effectively to global health threats posed by infectious diseases.
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