Laboratory testing at the Centers for Disease Control and Prevention (CDC) showed that recently discovered vials marked as “smallpox” contain vaccinia, the virus used in smallpox vaccine. There is no evidence that the vials contain variola virus, the cause of smallpox. CDC is in close contact with state and local health officials, law enforcement, and the World Health Organization about these findings.

On Nov. 15, 2021, the U.S. government was notified of the report of a small number of intact, frozen vials labeled “smallpox” discovered by a laboratory worker while cleaning out a freezer in a facility that conducts vaccine research in Pennsylvania.

The freezer facility was immediately secured and staff followed standard protocols for notifying CDC of such a potential discovery. The vials were sent securely to CDC for testing on Nov. 18 to determine what they contained. No one was exposed to contents of the vials.

Source: CDC