Vials marked as “smallpox” found this week at a commercial lab did not contain variola virus, the cause of smallpox, the Centers for Disease Control and Prevention announced Thursday night.
Testing conducted Thursday at the CDC showed that the vials contained vaccinia, the virus used in smallpox vaccine.
The U.S. government was notified Monday that a small number of frozen vials labeled “smallpox” were discovered by a laboratory worker cleaning out a freezer in a Pennsylvania facility that conducts vaccine research. Following the discovery, the freezer facility was secured and staff alerted the CDC.
The vials were sent to the CDC for testing, and no one was exposed to the contents of the vials.
The CDC also has been in close contact with state and local health officials, law enforcement and the World Health Organization about these findings.
Smallpox was declared officially eradicated on May 8, 1980.
There are only two locations that officially store and handle the variola virus under WHO supervision: the CDC and the State Research Center of Virology and Biotechnology in Koltsovo, Russia, according to the CDC.