Emergent BioSolutions said on Monday it would donate 50,000 doses of its smallpox vaccine to the Democratic Republic of the Congo and other impacted countries of Burundi, Kenya, Rwanda and Uganda to address the current mpox outbreak.

The World Health Organization last week declared mpox a global public health emergency for the second time in two years as a new variant of the virus, known as clade Ib, spread rapidly in Africa.

At least one person in Sweden has been confirmed with the infection, marking the first time the new variant has been seen outside of Africa.

Emergent's ACAM2000 vaccine, approved for smallpox, has been used as an mpox shot but the U.S. Food and Drug Administration is yet to approve its application for use against the virus.

According to the U.S. Centers for Disease Control and Prevention, ACAM2000, a live, replicating virus vaccine, has more known side effects and risks than Danish biotech Bavarian Nordic A/S's Jynneos vaccine, which is approved in the U.S. for both smallpox and mpox.

ACAM2000 is known to cause myocarditis/pericarditis - swelling in or around the heart muscle - in 1 in 175 new ACAM2000 vaccine recipients, according to the FDA.

Instead of an injection, the shot is given via a series of small pokes on the skin using a two-pronged needle.

The injection site forms a scab, which takes 2-4 weeks to heal. Until the scab falls off, it could spread live virus to other parts of the body or people.

ACAM2000 is not recommended for people with compromised immune systems, such as HIV.