Emergent Bio’s ACAM2000 is the second mpox vaccine to receive the FDA green light, following Bavarian Nordic’s Jynneos (marketed as Imvanex in the EU), which was approved in 2019. ACAM2000 was first approved by the FDA in 2007 for the prevention of smallpox in people who are at a higher risk of infection. While smallpox was eradicated in the early 1980s, ACAM2000 is stockpiled in the U.S. as the primary smallpox vaccine for use in a bioterrorism emergency.
The mpox virus and the smallpox virus are both part of the Poxvirus family, which is why ACAM2000 works against both viruses. The expanded approval of ACAM2000 for mpox is based on human safety data and data from an animal study, which showed that the vaccine effectively protects against mpox virus exposure.
Previously known as monkeypox, mpox is an infectious disease with symptoms including a painful rash, fever, and enlarged lymph nodes. The disease is seen as endemic to central and west Africa, however, in 2022 a global outbreak was declared a public health emergency of international concern by the WHO. This outbreak was caused by clade 2b of the mpox virus, while the latest outbreak – which was detected beyond Africa in August 2024 – is caused by clade 1b of the virus.
According to the WHO, more than 120 countries have reported over 100,000 laboratory-confirmed mpox cases and more than 220 deaths among confirmed cases between January 2022 and August 2024, although the numbers are thought to be much higher.
It is believed that clade 1b of the mpox virus is a more serious variant than the one that caused the previous outbreak. It has shown increased transmissibility through skin-to-skin contact, resulting in a higher number of severe infections and a greater mortality rate. The WHO is therefore calling for different measures, including vaccines, to combat the latest outbreak.
“[The] 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,” said Joe Papa, president and CEO of Emergent Bio in a press statement.
“We believe Emergent is poised to support the global response needed by actively engaging with world health leaders, as well as deploying products currently available in inventory based on the needs, as well as the ability to increase supply.”
Emergent Bio has also filed an Expression of Interest with the WHO so that the mpox vaccine can be on the Emergency Use Listing during the mpox outbreak. The company has also announced that it will donate 50,000 doses of the ACAM2000 vaccine for use in Central African countries.
