Second Generation Smallpox Vaccine Now Approved for Mpox Prevention

Emergent BioSolutions Inc. today announced that the U.S. Food and Drug Administration (FDA) approved the supplemental Biologics License Application for the expansion of the indication for the single-dose ACAM2000® Smallpox vaccine to include the prevention of mpox disease in individuals determined to be at high risk for mpox infection.

ACAM2000® is administered percutaneously via a bifurcated needle dipped into the vaccine solution. The skin is pricked several times in the upper arm with a droplet of the vaccine.

ACAM2000 was first approved by the FDA in 2007.

Dr. Amesh A. Adalja, FIDSA FACP FACEP & health security and emerging infectious diseases expert, Johns Hopkins Center for Health Security, commented in a press release on August 29, 2024, “ACAM2000®, a direct descendant of the Jenner vaccine (humanity’s first) which was used to eradicate smallpox, and now with the broadened indication, will be an invaluable tool in this endeavor.”

The FDA's labeling for ACAM2000® contains a contraindication for individuals with severe immunodeficiency. Severe localized or systemic infection with vaccinia (progressive vaccinia) may occur in persons with weakened immune systems. Individuals with severe immunodeficiency who are not expected to benefit from the vaccine should not receive ACAM2000®.

The risk of experiencing severe vaccination complications must be weighed against the risk of experiencing a potentially severe or fatal smallpox or mpox infection.

Additionally, there are warnings and precautions for 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 side effects may occur following primary or revaccination with live vaccinia virus vaccines, including ACAM2000®. These risks are increased in certain individuals and may result in severe disability, permanent neurological sequelae, and/or death.

As of late August 2024, four mpox vaccines are in use globally.