Emergent BioSolutions Inc. (NYSE: EBS) announced that the U.S. Food and Drug Administration (FDA) has approved the supplemental Biologics License Application (sBLA) for ACAM2000 (Smallpox and Mpox (Vaccinia) Vaccine, Live) to include the prevention of mpox disease in individuals determined to be at high risk for mpox infection. The approval, granted on August 29, 2024, is based on existing human safety data and results from a controlled animal study demonstrating the vaccine's effectiveness against mpox virus exposure.
ACAM2000 is administered as a single dose percutaneously, using a bifurcated needle dipped into the vaccine solution, followed by multiple skin pricks in the upper arm. Originally approved in 2007 for smallpox prevention, this expanded indication arrives as the global health community addresses a resurgence in mpox cases.
Addressing the Mpox Outbreak
"The FDA approval of ACAM2000 for immunization against mpox in high-risk individuals further strengthens and broadens our industry-leading smallpox portfolio," said Joe Papa, president and CEO of Emergent. He added that the approval comes at a critical time, as the global health community unites to ensure an effective response to the mpox outbreak. Emergent has filed an Expression of Interest with the World Health Organization (WHO) for ACAM2000 to be considered for Emergency Use Listing. The company will donate 50,000 doses of ACAM2000 for potential deployment in Central Africa.
Clinical Context and Disease Burden
Mpox, caused by a double-stranded DNA virus related to the virus that caused smallpox, is endemic to central and west Africa. In 2022, a global outbreak of clade II mpox led to over 95,000 cases across 115 non-endemic countries. The clade I variant is associated with more severe clinical outcomes and a higher case fatality rate. A recently identified clade Ib variant shows enhanced transmissibility, leading to increased cases, particularly in Central Africa, impacting children and families significantly. According to the WHO, clade I mpox tends to cause more severe infections and has a higher mortality rate than clade II mpox.
Safety Considerations
The labeling for ACAM2000 includes a contraindication for individuals with severe immunodeficiency. Severe localized or systemic infection with vaccinia (progressive vaccinia) may occur in persons with weakened immune systems. The risk for experiencing severe vaccination complications must be weighed against the risk for experiencing a potentially severe or fatal smallpox or mpox infection. Warnings and precautions include myocarditis, pericarditis, encephalitis, encephalomyelitis, encephalopathy, progressive vaccinia, generalized vaccinia, severe vaccinial skin infections, erythema multiforme major (including Stevens-Johnson Syndrome), eczema vaccinatum resulting in permanent sequelae or death, accidental eye infection (ocular vaccinia), which can cause ocular complications that may lead to blindness, and fetal death. These risks are increased in certain individuals and may result in severe disability, permanent neurological sequalae and/or death.
